Cyanine compound and photoelectric conversion element

ABSTRACT

Provided is a cyanine compound being bound counterions consisting of an anion and a cation, wherein the anion is represented by the following formula (I-1):wherein R1 and R2 each independently represent a hydrogen atom or a monovalent organic group; R3 and R4 each independently represent a monovalent group such as a phenyl group; X represents a hydrogen atom, a halogen atom or a monovalent organic group; and Y represents a divalent group such as a n-propenyl group.

TECHNICAL FIELD

The present invention relates to a cyanine compound and a photoelectricconversion element obtained using the same.

BACKGROUND ART

Techniques of converting visible light to electric signals or electricenergy by photoelectric conversion have heretofore been known. Theformer techniques are widely used in image sensors, and the lattertechniques are widely used in solar cells, etc. Also, techniques ofphotoelectrically converting near-infrared light are used in nightvision cameras, various sensors for distance measurement or the like,communication application, analysis apparatuses, etc.

Meanwhile, it is expected that new values can be imparted to theconventional techniques by using elements that are transmissive tovisible light, but selectively cause photoelectric conversion ofnear-infrared light. For example, such a photoelectric conversionelement disposed on the foreside of the light-receiving surface of animage sensor enables imaging and sensing (e.g., three-dimensionalmeasurement) to be performed at the same timing using the same element.As a result, the image sensor attains complex functions, downsizing, andcost reduction. Alternatively, such a photoelectric conversion elementdisposed on the foreside of a display accessorily confers electricenergy at the same time with image display outdoors, for example, andcan achieve power saving or battery-less approaches.

Laminated organic thin film-type elements are promising as theaforementioned photoelectric conversion elements which selectively causephotoelectric conversion of near-infrared light, in terms of the degreeof freedom of design of organic materials, small film thicknesses, andhigh sensitivity (quantum efficiency). For such a laminated organic thinfilm-type photoelectric conversion element, it is vital to use, in itsphotosensitive unit, a material that absorbs only near-infrared lightand has no or minimum absorption in the visible light region. Such anear-infrared absorptive material can also be used in opticalinformation recording media, organic solar cells, flash fusingphotosensitive materials, thermal shielding films, infrared cut filters,anti-counterfeit ink, or preform heating auxiliary agents intended forplastic bottles, in addition to those mentioned above.

As for examples of the laminated organic thin film-type element whichabsorbs only near-infrared light and is transmissive to a portion ofvisible light, for example, Patent Document 1 has reported an example inwhich a light is selectively absorbed by a material having a localmaximum absorption wavelength at 600 to 800 nm using a metalnaphthalocyanine derivative. Patent Documents 2 to 4 each describe aphotoelectric conversion element having a local maximum absorptionwavelength at or around 700 nm in the combined range of visible lightand near-infrared light. Particularly, Patent Document 3 states that amaterial whose absorption intensity at 400 to 550 nm is 1/10 or less ofabsorption intensity in the near-infrared region is provided. Non PatentDocument 1 describes a photoelectric conversion element in which acyanine color having specific absorption for near-infrared light is usedin a photosensitive layer.

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-Open No.    S63-186251-   Patent Document 2: Japanese Patent No. 5270114-   Patent Document 3: Japanese Patent Application Laid-Open No.    2012-169676-   Patent Document 4: Japanese Patent Application Laid-Open No.    2017-34112

Non Patent Document

-   Non Patent Document 1: Org. Lett., Vol. 11, No. 21, 2009

SUMMARY OF INVENTION Technical Problem

However, silicon metal, a typical material for photoelectric conversionelements, also has sensitivity to infrared light at or around awavelength of 600 to 800 nm, Therefore, the photoelectric conversionelements of Patent Documents 1 to 4 are less likely to demonstrate theirsuperiority over existing techniques. In the case of using aphotoelectric conversion element as infrared LED for use in imaging indark place, three-dimensional distance measurement, etc., or as alight-receiving element for infrared laser light emission, thewavelength of a light emission apparatus is generally a wavelength of800 nm or more. Hence, use of the elements of Patent Documents 1 to 4leads to factors for increasing cost, such as the need of using aspecial light emission apparatus. The material and the photoelectricconversion element of Non Patent Document 5 employ a cyanine colorhaving a maximum wavelength of 800 nm or more, and Non Patent Document 5describes its quantum efficiency. However, Non Patent Document 5 doesnot describe the durability performance (e.g., light resistance and heatresistance) of the color, which largely influences the productionprocess of the photoelectric conversion element or the resistance of theelement itself. Thus, the degree of feasibility is unknown.

The present invention has been made in light of at least a portion ofthese circumstances, and an object of the present invention is toprovide a novel cyanine compound that more selectively absorbs anincident light of more than 800 nm and is also excellent in lightresistance and heat resistance, and a photoelectric conversion elementobtained using the cyanine compound.

Solution to Problem

The present inventors have conducted diligent studies to attain theobject and consequently completed the present invention by finding anovel cyanine compound having a local maximum absorption wavelength ofmore than 800 nm.

Specifically, the present invention is as described below.

[1] A cyanine compound being bound counterions consisting of an anionand a cation, wherein the anion is represented by the following formula(I-1):

wherein R¹ and R² each independently represent a hydrogen atom or amonovalent organic group; R³ and R⁴ each independently represent amonovalent group represented by the following formula (I-1-1); Xrepresents a hydrogen atom, a halogen atom or a monovalent organicgroup; and Y represents a divalent group represented by the followingformula (I-1-2) or (I-1-3):

wherein R^(a), R^(b), R^(c), R^(d) and R^(e) each independentlyrepresent a hydrogen atom, a monovalent hydrocarbon group or amonovalent electron-withdrawing group; one or more of R^(a), R^(b),R^(c), R^(d) and R^(e) represent the monovalent electron-withdrawinggroup; and when one of R^(a), R^(b), R^(c), R^(d) and R^(e) is a halogenatom, one or more of the other moieties of R^(a), R^(b), R^(c), R^(d)and R^(e) represent the monovalent hydrocarbon group or the monovalentelectron-withdrawing group,

wherein R^(f), R^(g), R^(h), R^(i), R^(j) and R^(k) each independentlyrepresent a hydrogen atom, or a monovalent hydrocarbon group optionallyhaving oxygen atom(s), nitrogen atom(s) or sulfur atom(s), and

wherein R^(l), R^(m), R^(n) and R^(o) each independently represent ahydrogen atom, or a monovalent hydrocarbon group optionally havingoxygen atom(s), nitrogen atom(s) or sulfur atom(s).[2] The cyanine compound described above, wherein the cation containsone or more selected from the group consisting of an alkali metalcation, an alkaline earth metal cation, an ammonium cation, a sulfoniumcation, a phosphonium cation and cationic cyanine.[3] The cyanine compound described above, wherein the cation containsone or more selected from the group consisting of an alkali metalcation, an ammonium cation and cationic cyanine.[4] The cyanine compound described above, wherein the cationic cyanineis a cation represented by the following formula (I-2-1), (I-2-2),(I-2-3) or (I-2-4):

wherein

-   -   each E independently represents a carbon atom, a nitrogen atom,        an oxygen atom or a sulfur atom;    -   R^(p), R^(q), R^(r), R^(s), R^(t), R^(u), R^(v), R^(w) and R^(x)        each independently represent a hydrogen atom, a halogen atom, a        hydroxy group, a carboxy group, a nitro group, an amino group,        an amide group, an imide group, a cyano group, a silyl group,        -L¹, —S-L², —SS-L², —SO₂-L³, —N═N-L⁴, or one or more groups        selected from the group consisting of groups represented by the        following formulas (A), (B), (C), (D), (E), (F), (G) and (H)        having one or more combinations of R^(q) and R^(r), R^(s) and        R^(t), R^(t) and R^(u), R^(u) and R^(v), R^(v) and R^(w), and        R^(w) and R^(x) bonded to each other, wherein    -   the amino group, the amide group, the imide group and the silyl        group can be each further substituted by one or more groups L        selected from the group consisting of a monovalent aliphatic        hydrocarbon group having 1 to 12 carbon atoms, a monovalent        halogen-substituted alkyl group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms, a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms and a monovalent heterocyclic group having 3 to 14        carbon atoms;    -   each of the L¹ and the L⁴ is a monovalent aliphatic hydrocarbon        group having 1 to 12 carbon atoms, a monovalent        halogen-substituted alkyl group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms, a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms or a heterocyclic group having 3 to 14 carbon        atoms, each of which can be further substituted by the group(s)        L;    -   the L² is a hydrogen atom, or a monovalent aliphatic hydrocarbon        group having 1 to 12 carbon atoms, a monovalent        halogen-substituted alkyl group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms, a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms or a heterocyclic group having 3 to 14 carbon        atoms, each of which can be further substituted by the group(s)        L; and    -   the L³ is a hydroxy group, or a monovalent aliphatic hydrocarbon        group having 1 to 12 carbon atoms, a monovalent        halogen-substituted alkyl group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms, a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms or a heterocyclic group having 3 to 14 carbon        atoms, each of which can be further substituted by the group(s)        L;    -   Q¹ represents an acetyl group; and Q² represents a structure        represented by the following formula (q1), (q2) or (q3):

wherein the combination of R^(x) and R^(y) is a combination of R^(q) andR^(r), R^(s) and R^(t), R^(t) and R^(u), R^(u) and R^(v), R^(v) andR^(w), or R^(w) and R^(x);

-   -   R_(A), R_(B), R_(C), R_(D), R_(E), R_(F), R_(G), R_(H), R_(I),        R_(J), R_(K) and R_(L) each independently represent a hydrogen        atom, a halogen atom, a hydroxy group, a carboxy group, a nitro        group, an amino group, an amide group, an imide group, a cyano        group, a silyl group, -L¹, —S-L², —SS-L², —SO₂-L³ or —N═N-L⁴,        wherein L¹, L², L³ and L⁴ are as defined in L¹, L², L³ and L⁴ in        the formulas (I-2-1) and (I-2-2), and the amino group, the amide        group, the imide group and the silyl group can be substituted by        the group(s) L,

—C_(m)H_(m+1)  (q1)

—C_(a)H_(a+1)—OC_(b)H_(b+1)  (q2)

wherein m in the formula (q1) represents an integer of 1 to 5, and a andb in the formula (q2) each represent an integer of 1 to 5, and

wherein n represents an integer of 1 to 5; T₁, T₂, T₃, T₄ and T₅ eachindependently represent a hydrogen atom or —OC_(p)H_(p+1); and prepresents an integer of 1 to 5.[5] The cyanine compound described above, wherein the monovalent organicgroup represented by each of the R¹ and the R² is a monovalent aliphatichydrocarbon group having 1 to 12 carbon atoms, a monovalenthalogen-substituted alkyl group having 1 to 12 carbon atoms, amonovalent alicyclic hydrocarbon group having 3 to 14 carbon atoms, amonovalent aromatic hydrocarbon group having 6 to 14 carbon atoms or aheterocyclic group having 3 to 14 carbon atoms, each of which can befurther substituted by a monovalent hydrocarbon group or a monovalentelectron-withdrawing group.[6] The cyanine compound described above, wherein the R¹ and the R² areeach independently a hydrogen atom, a monovalent aliphatic hydrocarbongroup having 1 to 3 carbon atoms or a monovalent group represented bythe formula (I-1-1).[7] The cyanine compound described above, wherein

-   -   the monovalent organic group represented by the X represents a        hydroxy group, a carboxy group, a nitro group, an amino group,        an amide group, an imide group, a cyano group, a silyl group,        -L¹, —S-L², —SS-L³, —SO₂-L³, or —N═N-L⁴, wherein    -   the amino group, the amide group, the imide group and the silyl        group can be each further substituted by one or more groups L        selected from the group consisting of a monovalent aliphatic        hydrocarbon group having 1 to 12 carbon atoms, a monovalent        halogen-substituted alkyl group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms, a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms and a monovalent heterocyclic group having 3 to 14        carbon atoms;    -   each of the L¹ and the L⁴ is a monovalent aliphatic hydrocarbon        group having 1 to 12 carbon atoms, a monovalent        halogen-substituted alkyl group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms, a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms or a heterocyclic group having 3 to 14 carbon        atoms, each of which can be further substituted by the group(s)        L;    -   the L² is a hydrogen atom, or a monovalent aliphatic hydrocarbon        group having 1 to 12 carbon atoms, a monovalent        halogen-substituted alkyl group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms, a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms or a heterocyclic group having 3 to 14 carbon        atoms, each of which can be further substituted by the group(s)        L; and    -   the L³ is a hydroxy group, or a monovalent aliphatic hydrocarbon        group having 1 to 12 carbon atoms, a monovalent        halogen-substituted alkyl group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms, a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms or a heterocyclic group having 3 to 14 carbon        atoms, each of which can be further substituted by the group(s)        L.        [8] The cyanine compound described above, wherein the X is a        halogen atom.        [9] The cyanine compound described above, wherein the monovalent        hydrocarbon group represented by each of the R^(a), the R^(b),        the R^(c), the R^(d) and the R^(e) is a monovalent aliphatic        hydrocarbon group having 1 to 12 carbon atoms, a monovalent        alicyclic hydrocarbon group having 3 to 14 carbon atoms or a        monovalent aromatic hydrocarbon group having 6 to 14 carbon        atoms, each of which can be further substituted by one or more        groups selected from the group consisting of a monovalent        aliphatic hydrocarbon group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms and a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms.        [10] The cyanine compound described above, wherein the        monovalent electron-withdrawing group represented by each of the        R^(a), the R^(b), the R^(c), the R^(d) and the R^(e) is a        halogen atom, a carboxy group, a nitro group, a cyano group, a        group represented by —COR, a group represented by —CONR₂, a        group represented by —SO₂R or a group represented by —SO₃R,        wherein the R is as defined in the monovalent hydrocarbon group        or a hydrogen atom.        [11] The cyanine compound described above, wherein the R^(a),        the R^(b), the R^(c), the R^(d) and the R^(e) each independently        represent a hydrogen atom or a halogen atom, and two or more of        R^(a), R^(b), R^(c), R^(d) and R^(e) are halogen atoms.        [12] The cyanine compound described above, wherein the        monovalent hydrocarbon group optionally having oxygen atom(s),        nitrogen atom(s) or sulfur atom(s), represented by each of the        R^(f), the R^(g), the R^(h), the R^(i), the R^(j), the R^(k),        the R^(l), the R^(m), the R^(n) and the R^(o) is a monovalent        aliphatic hydrocarbon group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms or a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms, each of which can be further substituted by one or        more groups selected from the group consisting of a monovalent        aliphatic hydrocarbon group having 1 to 12 carbon atoms, a        monovalent alicyclic hydrocarbon group having 3 to 14 carbon        atoms and a monovalent aromatic hydrocarbon group having 6 to 14        carbon atoms, each of which optionally has oxygen atom(s),        nitrogen atom(s) or sulfur atom(s).        [13] The cyanine compound described above, wherein R^(f), R^(g),        R^(h), R^(i), R^(j), R^(k), R^(l), R^(m), R^(n) and R^(o) each        independently represent a hydrogen atom, or a monovalent        aliphatic hydrocarbon group having 1 to 12 carbon atoms.        [14] A photoelectric conversion element including an infrared        photoelectric conversion unit including a pair of electrodes and        an organic infrared photoelectric conversion film disposed        between the pair of electrodes, wherein    -   the organic infrared photoelectric conversion film contains the        cyanine compound described above.        [15] The photoelectric conversion element described above,        wherein the organic infrared photoelectric conversion film        contains an organic n-type semiconductor and/or an organic        p-type semiconductor.        [16] The photoelectric conversion element described above,        wherein the infrared photoelectric conversion unit includes one        or more selected from the group consisting of a hole transport        layer, an electron transport layer, a hole blocking layer, and        an electron blocking layer between the electrode and the organic        infrared photoelectric conversion film.        [17] The photoelectric conversion element described above,        wherein in the infrared photoelectric conversion unit, a local        maximum absorption wavelength and a maximum absorption        wavelength of optical absorption spectra in the infrared region        are 800 nm or more and 2500 nm or less.        [18] The photoelectric conversion element described above,        wherein the photoelectric conversion element further includes a        visible photoelectric conversion unit having sensitivity to a        light in the visible region.

Advantageous Effects of Invention

The present invention can provide a cyanine compound that moreselectively absorbs an incident light of more than 800 nm and is alsoexcellent in light resistance and heat resistance, and a photoelectricconversion element obtained using the cyanine compound.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 is a cross-sectional schematic view partially showing one exampleof the photoelectric conversion unit of the present invention.

FIG. 2 shows absorption spectra as to one example of the cyaninecompound of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the mode for carrying out the present invention(hereinafter, simply referred to as the “present embodiment”) will bedescribed in detail with reference to the drawings, if necessary.However, the present invention is not limited by the present embodimentdescribed below. Various changes or modifications can be made in thepresent invention without departing from the spirit of the presentinvention. In the drawings, the same numerals or symbols will be used todesignate the same components, so that the description will be omitted.Positional relationship indicated by terms such as “up”, “down”, “right”and “left” is based on the positional relationship shown in thedrawings, unless otherwise specified. The dimensional ratios of thedrawings are not limited to the shown ratios.

(Cyanine Compound)

The cyanine compound of the present embodiment is a cyanine compoundbeing bound counterions consisting of an anion and a cation, wherein theanion is represented by the following formula (I-1):

In the formula (I-1), R¹ and R² each independently represent a hydrogenatom or a monovalent organic group; R³ and R⁴ each independentlyrepresent a monovalent group represented by the following formula(I-1-1); X represents a hydrogen atom, a halogen atom or a monovalentorganic group; and Y represents a divalent group represented by thefollowing formula (I-1-2) or (I-1-3):

In the formula (I-1-1), R^(a), R^(b), R^(c), R^(d) and R^(e) eachindependently represent a hydrogen atom, a monovalent hydrocarbon groupor a monovalent electron-withdrawing group; one or more of R^(a), R^(b),R^(c), R^(d) and R^(e) represent the monovalent electron-withdrawinggroup; and when one of R^(a), R^(b), R^(c), R^(d) and R^(e) is a halogenatom, one or more of the other moieties of R^(a), R^(b), R^(c), R^(d)and R^(e) represent the monovalent hydrocarbon group or the monovalentelectron-withdrawing group.

In the formula (I-1-2), R^(f), R^(g), R^(h), R^(i), R^(j) and R^(k) eachindependently represent a hydrogen atom, or a monovalent hydrocarbongroup optionally having oxygen atom(s), nitrogen atom(s) or sulfuratom(s).

In the formula (I-1-3), R^(l), R^(m), R^(n) and R^(o) each independentlyrepresent a hydrogen atom, or a monovalent hydrocarbon group optionallyhaving oxygen atom(s), nitrogen atom(s) or sulfur atom(s).

(Anion)

The anion according to the present embodiment is represented by theformula (I-1). Each of R¹, R², R³, R⁴, X and Y preferably has a total of60 or less carbon atoms, more preferably 50 or less carbon atoms,particularly preferably 40 or less carbon atoms, includingsubstituent(s). When the number of carbon atoms falls within this range,the cyanine compound is more easily synthesized, while absorptionintensity per unit weight tends to be high.

Examples of the monovalent organic group represented by each of R¹ andR² include, but are not particularly limited, a monovalent aliphatichydrocarbon group having 1 to 12 carbon atoms, a monovalenthalogen-substituted alkyl group having 1 to 12 carbon atoms, amonovalent alicyclic hydrocarbon group having 3 to 14 carbon atoms, amonovalent aromatic hydrocarbon group having 6 to 14 carbon atoms or aheterocyclic group having 3 to 14 carbon atoms, each of which can befurther substituted by a monovalent hydrocarbon group or a monovalentelectron-withdrawing group.

Examples of the monovalent aliphatic hydrocarbon group having 1 to 12carbon atoms include: alkyl groups such as a methyl group (Me), an ethylgroup (Et), a n-propyl group (n-Pr), an isopropyl group (i-Pr), an-butyl group (n-Bu), a sec-butyl group (s-Bu), a tert-butyl group(t-Bu), a pentyl group, a hexyl group, an octyl group, a nonyl group, adecyl group and a dodecyl group; alkenyl groups such as a vinyl group, a1-propenyl group, a 2-propenyl group, a butenyl group, a 1,3-butadienylgroup, a 2-methyl-1-propenyl group, a 2-pentenyl group, a hexenyl groupand an octenyl group; and alkynyl groups such as an ethynyl group, apropynyl group, a butynyl group, a 2-methyl-1-propynyl group, a hexynylgroup and an octynyl group. Among them, a monovalent aliphatichydrocarbon group having 1 to 3 carbon atoms is preferred. Specifically,an alkyl group having 1 to 3 carbon atoms, such as a methyl group (Me),an ethyl group (Et), a n-propyl group (n-Pr) and an isopropyl group(i-Pr) is preferred.

Examples of the monovalent halogen-substituted alkyl group having 1 to12 carbon atoms include monovalent halogen-substituted alkyl groupshaving 1 to 3 carbon atoms. More specific examples of such ahalogen-substituted alkyl group include a trichloromethyl group, atrifluoromethyl group, a 1,1-dichloroethyl group, a pentachloroethylgroup, a pentafluoroethyl group, a heptachloropropyl group and aheptafluoropropyl group.

Examples of the monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms include monovalent alicyclic hydrocarbon groups having 4 to10 carbon atoms. More specific examples of such an alicyclic hydrocarbongroup include: cycloalkyl groups such as a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group; and polycyclic alicyclic groups such as a norbornanegroup and an adamantane group.

Examples of the monovalent aromatic hydrocarbon group having 6 to 14carbon atoms include a phenyl group, a tolyl group, a xylyl group, amesityl group, a cumenyl group, a 1-naphthyl group, a 2-naphthyl group,an anthracenyl group, a phenanthryl group, an acenaphthyl group, aphenalenyl group, a tetrahydronaphthyl group, an indanyl group and abiphenylyl group. This aromatic hydrocarbon group may be a monovalentgroup represented by the formula (I-1-1) mentioned later in detail. Inthis case, R¹ and R³ or R² and R⁴ may be the same with or different fromeach other.

Examples of the heterocyclic group having 3 to 14 carbon atoms includegroups consisting of heterocyclic rings such as furan, thiophene,pyrrole, pyrazole, imidazole, triazole, oxazole, oxadiazole, thiazole,thiadiazole, indole, indoline, indolenine, benzofuran, benzothiophene,carbazole, dibenzofuran, dibenzothiophene, pyridine, pyrimidine,pyrazine, pyridazine, quinoline, isoquinoline, acridine, morpholine andphenazine.

Examples of the monovalent hydrocarbon group serving as a substituentinclude, but are not particularly limited to, monovalent aliphatichydrocarbon groups having 1 to 12 carbon atoms, monovalent alicyclichydrocarbon groups having 3 to 14 carbon atoms, and monovalent aromatichydrocarbon groups having 6 to 14 carbon atoms. Each of their examplesor preferred forms is the same as those described above, so that thedescription will be omitted here.

The monovalent electron-withdrawing group serving as a substituent isnot particularly limited as long as it is a monovalent group thatexhibits electron-withdrawing properties in the anion according to thepresent embodiment. In this context, whether or not the substituent isan “electron-withdrawing group” can be determined as follows: an anionmolecule having the substituent is structurally optimized by molecularsimulation using density functional formalism (e.g., molecularsimulation using quantum chemical calculation program Gaussianmanufactured by Gaussian, Inc.) to determine electron affinity orionization energy. This is referred to as pre-substitution electronaffinity or ionization energy. Subsequently, electron affinity orionization energy is determined in the same manner as above as to ananion molecule obtained by substituting the substituent in the anionmolecule by a hydrogen atom or a monovalent hydrocarbon group. This isreferred to as post-substitution electron affinity or ionization energy.When the post-substitution electron affinity or ionization energy islarger than the pre-substitution electron affinity or ionization energy,this substituent is determined as an electron-withdrawing group. Such amonovalent electron-withdrawing group will be mentioned later in detail,so that the description will be omitted here.

In the monovalent group represented by the formula (I-1-1), R^(a),R^(b), R^(c), R^(d) and R^(e) (hereinafter, simply referred to as “R^(a)to R^(e)”) each independently represent a hydrogen atom, a monovalenthydrocarbon group or a monovalent electron-withdrawing group. One ormore of R^(a) to R^(e) represent the monovalent electron-withdrawinggroup, i.e., the monovalent group represented by the formula (I-1-1)inevitably has a monovalent electron-withdrawing group. When one ofR^(a) to R^(e) is a halogen atom, one or more of the other moieties ofR^(a) to R^(e) represent the monovalent hydrocarbon group or themonovalent electron-withdrawing group. Specifically, when one of R^(a)to R^(e) is a halogen atom, there is no form in which all the othermoieties of R^(a) to R^(e) are hydrogen atoms. Examples of themonovalent hydrocarbon group include the same as those listed above, sothat the description will be omitted here.

The monovalent electron-withdrawing group is not particularly limited aslong as it is a monovalent group that exhibits electron-withdrawingproperties in the anion according to the present embodiment. Examples ofsuch a monovalent electron-withdrawing group include a halogen atom, acarboxy group (—COOH), a nitro group (—NO₂), a cyano group (—CN), agroup represented by —COR, a group represented by —CONR₂, a grouprepresented by —SO₂R or a group represented by —SO₃R. In this context, Ris a hydrogen atom or a monovalent hydrocarbon group. The monovalenthydrocarbon group is as defined in the monovalent hydrocarbon groupdescribed above, so that the detailed description will be omitted here.

Examples of the halogen atom include a fluorine atom (F), a chlorineatom (Cl), a bromine atom (Br) and an iodine atom (I).

Examples of the group represented by —COR (acyl group) include an acetylgroup, a propionyl group, a butyryl group, an isobutyryl group, abenzoyl group, an acryloyl group and a methacryloyl group. In thiscontext, the number of carbon atoms in R may be 1 to 6.

Examples of the group represented by —CONR₂ (amide group) include anamide group, a methylamide group, a dimethylamide group, a diethylamidegroup, a dipropylamide group, a diisopropylamide group, and adibutylamide group. In this context, the group represented by —CONR₂ maybe lactam in which one of the R moieties is bonded to a carbon atom of acarboxy group. Examples of the lactam include an α-lactam group, aβ-lactam group, a γ-lactam group, and a δ-lactam group. In this context,the number of carbon atoms in R may be 1 to 4.

Examples of the group represented by —SO₂R include a mesyl group, anethylsulfonyl group, a n-butylsulfonyl group, a phenylsulfonyl group anda p-toluenesulfonyl group. In this context, the number of carbon atomsin R may be 1 to 7.

Examples of the group represented by —SO₃R include a sulfo group(—SO₃H), a methylsulfonic acid group (—SO₃CH₃), an ethylsulfonic acidgroup (—SO₃C₂H₅), a n-butylsulfonic acid group (—SO₃C₃H₇), and aphenylsulfonic acid group (—SO₃C₆H₅). In this context, the number ofcarbon atoms in R may be 1 to 6.

In the present embodiment, preferably two or more of R^(a) to R^(e) inthe anion are electron-withdrawing groups, more preferably three or morethereof are electron-withdrawing groups, and particularly preferably allof them are electron-withdrawing groups, from the viewpoint of stillmore selectively absorbing an incident light of more than 800 nm, From asimilar viewpoint, the electron-withdrawing group is preferably ahalogen atom. When two or more of R^(a) to R^(e) areelectron-withdrawing groups, more preferably all of them are halogenatoms.

The combination of R^(a) to R^(e) in the formula (I-1-1) may be anycombination of the substituents listed above as long as it is acombination in which, when one or more of R^(a) to R^(e) represent themonovalent electron-withdrawing group and one of R^(a) to R^(e) is ahalogen atom, one or more of the other moieties of R^(a) to R^(e)represent the monovalent hydrocarbon group or the monovalentelectron-withdrawing group.

X represents a hydrogen atom, a halogen atom or a monovalent organicgroup. Among them, a halogen atom is preferred. Examples of the halogenatom include the same as those listed above, so that the descriptionwill be omitted here.

Examples of the monovalent organic group represented by X include, butare not particularly limited, a hydroxy group, a carboxy group, a nitrogroup, an amino group, an amide group, an imide group, a cyano group, asilyl group, -L¹, —S-L², —SS-L³, —SO₂-L³, or —N═N-L⁴. The amino group,the amide group, the imide group and the silyl group can be each furthersubstituted by one or more groups L selected from the group consistingof a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms,a monovalent halogen-substituted alkyl group having 1 to 12 carbonatoms, a monovalent alicyclic hydrocarbon group having 3 to 14 carbonatoms, a monovalent aromatic hydrocarbon group having 6 to 14 carbonatoms and a monovalent heterocyclic group having 3 to 14 carbon atoms.

Each of L¹ and L⁴ is a monovalent aliphatic hydrocarbon group having 1to 12 carbon atoms, a monovalent halogen-substituted alkyl group having1 to 12 carbon atoms, a monovalent alicyclic hydrocarbon group having 3to 14 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to14 carbon atoms or a heterocyclic group having 3 to 14 carbon atoms,each of which can be further substituted by the group(s) L. L² is ahydrogen atom, or a monovalent aliphatic hydrocarbon group having 1 to12 carbon atoms, a monovalent halogen-substituted alkyl group having 1to 12 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to14 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms or a heterocyclic group having 3 to 14 carbon atoms, eachof which can be further substituted by the group(s) L. L³ is a hydroxygroup, or a monovalent aliphatic hydrocarbon group having 1 to 12 carbonatoms, a monovalent halogen-substituted alkyl group having 1 to 12carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms or a monovalent heterocyclic group having 3 to 14 carbonatoms, each of which can be further substituted by the group(s) L.

Examples of the monovalent aliphatic hydrocarbon group having 1 to 12carbon atoms, the monovalent halogen-substituted alkyl group having 1 to12 carbon atoms, the monovalent alicyclic hydrocarbon group having 3 to14 carbon atoms, the monovalent aromatic hydrocarbon group having 6 to14 carbon atoms and the monovalent heterocyclic group having 3 to 14carbon atoms include the same as those listed above, so that thedescription will be omitted here.

The monovalent aliphatic hydrocarbon group having 1 to 12 carbon atomswhich can be further substituted by the group(s) L is preferably amethyl group, an ethyl group, a n-propyl group, an isopropyl group, an-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, ahexyl group, an octyl group, a 4-phenylbutyl group, or a2-cyclohexylethyl, more preferably a methyl group, an ethyl group, an-propyl group, an isopropyl group, a n-butyl group, a sec-butyl group,a tert-butyl group, or a hexyl group.

The monovalent halogen-substituted alkyl group having 1 to 12 carbonatoms which can be further substituted by the group(s) L is preferably atrichloromethyl group, a pentachloroethyl group, a trifluoromethylgroup, a pentafluoroethyl group, or a5-cyclohexyl-2,2,3,3-tetrafluoropentyl group, more preferably atrichloromethyl group, a pentachloroethyl group, a trifluoromethylgroup, or a pentafluoroethyl group.

The monovalent alicyclic hydrocarbon group having 3 to 14 carbon atomswhich can be further substituted by the group(s) L is preferably acyclobutyl group, a cyclopentyl group, a cyclohexyl group, a4-ethylcyclohexyl group, a cyclooctyl group, or a 4-phenylcycloheptylgroup, more preferably a cyclopentyl group, a cyclohexyl group, or a4-ethylcyclohexyl group.

The monovalent aromatic hydrocarbon group having 6 to 14 carbon atomswhich can be further substituted by the group(s) L is preferably aphenyl group, a 1-naphthyl group, a 2-naphthyl group, a tolyl group, axylyl group, a mesityl group, a cumenyl group, a 3,5-di-tert-butylphenylgroup, a 4-cyclopentylphenyl group, a 2,3,6-triphenylphenyl group, or a2,3,4,5,6-pentaphenylphenyl group, more preferably a phenyl group, atolyl group, a xylyl group, a mesityl group, a cumenyl group, or a2,3,4,5,6-pentaphenylphenyl group.

The monovalent heterocyclic group having 3 to 14 carbon atoms which canbe further substituted by the group(s) L is preferably a groupconsisting of furan, thiophene, pyrrole, indole, indoline, indolenine,benzofuran, benzothiophene, or morpholine, more preferably a groupconsisting of furan, thiophene, pyrrole, or morpholine.

The monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms,the monovalent halogen-substituted alkyl group having 1 to 12 carbonatoms, the monovalent alicyclic hydrocarbon group having 3 to 14 carbonatoms, the monovalent aromatic hydrocarbon group having 6 to 14 carbonatoms or the heterocyclic group having 3 to 14 carbon atoms, each ofwhich can be further substituted by the group(s) L, may further have oneor more selected from the group consisting of a halogen atom, a sulfogroup, a hydroxy group, a cyano group, a nitro group, a carboxy group, aphosphoric acid group and an amino group. Examples thereof include a4-sulfobutyl group, a 4-cyanobutyl group, a 5-carboxypentyl group, a5-aminopentyl group, a 3-hydroxypropyl group, a 2-phosphorylethyl group,a 6-amino-2,2-dichlorohexyl group, a 2-chloro-4-hydroxybutyl group, a2-cyanocyclobutyl group, a 3-hydroxycyclopentyl group, a3-carboxycyclopentyl group, a 4-aminocyclohexyl group, a4-hydroxycyclohexyl group, a 4-hydroxyphenyl group, a 2-hydroxynaphthylgroup, a 4-aminophenyl group, a 2,3,4,5,6-pentafluorophenyl group, a4-nitrophenyl group, a group consisting of 3-methylpyrrole, a2-hydroxyethoxy group, a 3-cyanopropoxy group, a 4-fluorobenzoyl group,a 2-hydroxyethoxycarbonyl group, and a 4-cyanobutoxycarbonyl group.

Examples of the amino group optionally having the group(s) L include anamino group, an ethylamino group, a dimethylamino group, amethylethylamino group, a dibutylamino group, and a diisopropylaminogroup.

Examples of the amide group optionally having the group(s) L include anamide group, a methylamide group, a dimethylamide group, a diethylamidegroup, a dipropylamide group, a diisopropylamide group, a dibutylamidegroup, an α-lactam group, a β-lactam group, a γ-lactam group, and aδ-lactam group.

Examples of the imide group optionally having the group(s) L include animide group, a methylimide group, an ethylimide group, a diethylimidegroup, a dipropylimide group, a diisopropylimide group, and adibutylimide group.

Examples of the silyl group optionally having the group(s) L include atrimethylsilyl group, a tert-butyldimethylsilyl group, a triphenylsilylgroup, and a triethylsilyl group.

Y represents a divalent group represented by the formula (I-1-2) or(I-1-3). In the formula (I-1-2), R^(f), R^(g), R^(h), R^(i), R^(j) andR^(k) (hereinafter, simply referred to as “R^(f) to R^(k)”) eachindependently represent a hydrogen atom, or a monovalent hydrocarbongroup optionally having oxygen atom(s), nitrogen atom(S) or sulfuratom(s). In the formula (I-1-3), R^(l), R^(m), R^(n) andR^(o)(hereinafter, simply referred to as “R^(l) to R^(o)”) eachindependently represent a hydrogen atom, or a monovalent hydrocarbongroup optionally having oxygen atom(s), nitrogen atom(s) or sulfuratom(s).

Examples of the monovalent hydrocarbon group optionally having oxygenatom(s), nitrogen atom(s) or sulfur atom(s) include a monovalentaliphatic hydrocarbon group having 1 to 12 carbon atoms, a monovalentalicyclic hydrocarbon group having 3 to 14 carbon atoms or a monovalentaromatic hydrocarbon group having 6 to 14 carbon atoms, each of whichcan be further substituted by one or more groups selected from the groupconsisting of a monovalent aliphatic hydrocarbon group having 1 to 12carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms and a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms, each of which optionally has oxygen atom(s), nitrogenatom(s) or sulfur atom(s).

Examples of the monovalent hydrocarbon group without having an oxygenatom, a nitrogen atom and a sulfur atom, more specifically, themonovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms, themonovalent alicyclic hydrocarbon group having 3 to 14 carbon atoms andthe monovalent aromatic hydrocarbon group having 6 to 14 carbon atoms,as well as the monovalent aliphatic hydrocarbon group having 1 to 12carbon atoms, the monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms and the monovalent aromatic hydrocarbon group having 6 to14 carbon atoms, each serving as a substituent include the same as thoselisted about the monovalent hydrocarbon group described above, so thatthe description will be omitted here.

Examples of the monovalent hydrocarbon group having an oxygen atom, anitrogen atom or a sulfur atom include a monovalent aliphatichydrocarbon group having 1 to 12 carbon atoms, a monovalent alicyclichydrocarbon group having 3 to 14 carbon atoms or a monovalent aromatichydrocarbon group having 6 to 14 carbon atoms, each of which can befurther substituted by one or more groups selected from the groupconsisting of a monovalent aliphatic hydrocarbon group having 1 to 12carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms and a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms (hereinafter, simply referred to as “substituent(s)” in thedescription of Y), each of which has one or more selected from the groupconsisting of an oxygen atom, a nitrogen atom and a sulfur atom.Examples of the case of having an oxygen atom include the case of havinga hydroxy group, an ether group, a carbonyl group or a carboxy group.Examples of the case of having a nitrogen atom include the case ofhaving a cyano group or an amino group. Examples of the case of having asulfur atom include the case of having a thioether group. Examples ofthe case of having an oxygen atom and a nitrogen atom include the caseof having a nitro group. Examples of the case of having an oxygen atomand a sulfur atom include the case of having a sulfo group.

The hydrogen atom, or the monovalent hydrocarbon group optionally havingoxygen atom(s), nitrogen atom(s) or sulfur atom(s) is preferably ahydrogen atom, or a monovalent aliphatic hydrocarbon group having 1 to12 carbon atoms. The monovalent aliphatic hydrocarbon group having 1 to12 carbon atoms is more preferably a monovalent aliphatic hydrocarbongroup having 1 to 6 carbon atoms, further preferably a monovalentaliphatic hydrocarbon group having 1 to 4 carbon atoms.

Preferred examples of the combinations of R^(f) to R^(k) and R^(l) toR^(o) include combinations shown in the following table.

TABLE 1 R^(f) R^(g) R^(h) R^(i) R^(j) R^(k) H H H H H H H H t-Bu H H H HH Me H H H H H Me Me H H H H Et H H H R^(l) R^(m) R^(n) R^(o) H H H H HMe H Me

(Cation)

The cation according to the present embodiment is not particularlylimited and preferably contains one or more selected from the groupconsisting of an alkali metal cation, an alkaline earth metal cation, anammonium cation, a sulfonium cation, a phosphonium cation and cationiccyanine. The cation more preferably contains one or more selected fromthe group consisting of an alkali metal cation, an ammonium cation andcationic cyanine.

Examples of the alkali metal cation include a lithium cation (Li⁺), asodium cation (Na⁺), a potassium cation (K⁺), a rubidium cation (Rb⁺)and a cesium cation (Cs⁺).

Examples of the alkaline earth metal cation include a beryllium cation(Be²⁺), a magnesium cation (Mg²⁺), a calcium cation (Ca²⁺), a strontiumcation (Sr²⁺) and a barium cation (Ba²⁺).

The ammonium cation includes an ammonium ion (NH₄ ⁺), primary ammoniumcations (NH₃R⁺), secondary ammonium cations (NH₂R₂ ⁺), tertiary ammoniumcations (NHR₃ ⁺) and quaternary ammonium cations (HR₄ ⁺) such astetraalkylammonium cations typified by a tetrabutylammonium cation. Inthis context, R represents a monovalent aliphatic hydrocarbon grouphaving 1 to 12 carbon atoms, such as an alkyl group having 1 to 12carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms.

The sulfonium cation includes a sulfonium ion (SH₃ ⁺), primary sulfoniumcations (SH₂R⁺), secondary sulfonium cations (SHR₂ ⁺) and tertiarysulfonium cations (SR₃ ⁺). In this context, R represents a monovalentaliphatic hydrocarbon group having 1 to 12 carbon atoms, such as analkyl group having 1 to 12 carbon atoms, a monovalent alicyclichydrocarbon group having 3 to 14 carbon atoms, or a monovalent aromatichydrocarbon group having 6 to 14 carbon atoms.

The phosphonium cation includes a phosphonium ion (PH₄ ⁺), primaryphosphonium cations (PH₃R⁺), secondary phosphonium cations (PH₂R₂ ⁺),tertiary phosphonium cations (PHR₃ ⁺) and quaternary phosphonium cations(PR₄ ⁺). In this context, R represents a monovalent aliphatichydrocarbon group having 1 to 12 carbon atoms, such as an alkyl grouphaving 1 to 12 carbon atoms, a monovalent alicyclic hydrocarbon grouphaving 3 to 14 carbon atoms, or a monovalent aromatic hydrocarbon grouphaving 6 to 14 carbon atoms.

Examples of the cationic cyanine include cations represented by thefollowing formula (I-2-1), (I-2-2), (I-2-3) or (I-2-4):

In the formulas (I-2-1), (I-2-2), (I-2-3) and (I-2-4), each Eindependently represents a carbon atom, a nitrogen atom, an oxygen atomor a sulfur atom, R^(p), R^(q), R^(r), R^(s), R^(t), R^(u), R^(v), R^(w)and R^(x) each independently represent a hydrogen atom, a halogen atom,a hydroxy group, a carboxy group, a nitro group, an amino group, anamide group, an imide group, a cyano group, a silyl group, -L¹, —S-L²,—SS-L², —SO₂-L³, —N═N-L⁴, or one or more groups selected from the groupconsisting of groups represented by the following formulas (A), (B),(C), (D), (E), (F), (G) and (H) having one or more combinations of R^(q)and R^(r), R^(s) and R^(t), R^(t) and R^(u), R^(u) and R^(v), R^(v) andR^(w), and R^(w) and R^(x) bonded to each other.

The amino group, the amide group, the imide group and the silyl groupcan be each further substituted by one or more groups L selected fromthe group consisting of a monovalent aliphatic hydrocarbon group having1 to 12 carbon atoms, a monovalent halogen-substituted alkyl grouphaving 1 to 12 carbon atoms, a monovalent alicyclic hydrocarbon grouphaving 3 to 14 carbon atoms, a monovalent aromatic hydrocarbon grouphaving 6 to 14 carbon atoms and a monovalent heterocyclic group having 3to 14 carbon atoms.

Each of L¹ and L⁴ is a monovalent aliphatic hydrocarbon group having 1to 12 carbon atoms, a monovalent halogen-substituted alkyl group having1 to 12 carbon atoms, a monovalent alicyclic hydrocarbon group having 3to 14 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to14 carbon atoms or a heterocyclic group having 3 to 14 carbon atoms,each of which can be further substituted by the group(s) L.

L² is a hydrogen atom, or a monovalent aliphatic hydrocarbon grouphaving 1 to 12 carbon atoms, a monovalent halogen-substituted alkylgroup having 1 to 12 carbon atoms, a monovalent alicyclic hydrocarbongroup having 3 to 14 carbon atoms, a monovalent aromatic hydrocarbongroup having 6 to 14 carbon atoms or a heterocyclic group having 3 to 14carbon atoms, each of which can be further substituted by the group(s)L.

L³ is a hydroxy group, or a monovalent aliphatic hydrocarbon grouphaving 1 to 12 carbon atoms, a monovalent halogen-substituted alkylgroup having 1 to 12 carbon atoms, a monovalent alicyclic hydrocarbongroup having 3 to 14 carbon atoms, a monovalent aromatic hydrocarbongroup having 6 to 14 carbon atoms or a heterocyclic group having 3 to 14carbon atoms, each of which can be further substituted by the group(s)L.

Q¹ represents an acetyl group, and Q² represents a structure representedby the following formula (q1), (q2) or (q3):

In the formulas (A), (B), (C), (D), (E), (F), (G) and (H), thecombination of R^(x) and R^(y) is a combination of R^(q) and R^(r),R^(s) and R^(t), R^(t) and R^(u), R^(u) and R^(v), R^(v) and R^(w), orR^(w) and R^(x).

R_(A), R_(B), R_(C), R_(D), R_(E), R_(F), R_(G), R_(H), R_(I), R_(J),R_(K) and R_(L) each independently represent a hydrogen atom, a halogenatom, a hydroxy group, a carboxy group, a nitro group, an amino group,an amide group, an imide group, a cyano group, a silyl group, -L¹,—S-L², —SS-L², —SO₂-L³ or —N═N-L⁴. L¹, L², L³ and L⁴ are as defined inL¹, L², L³ and L⁴ in the formulas (I-2-1) and (I-2-2), so that thedetailed description will be omitted here. The amino group, the amidegroup, the imide group and the silyl group can be each substituted bythe group(s) L.

—C_(m)H_(m+1)  (q1)

—C_(a)H_(a+1)—OC_(b)H_(b+1)  (q2)

In the formula (q1), m represents an integer of 1 to 5. In the formula(q2), a and b each represent an integer of 1 to 5.

In the formula (q3), n represents an integer of 1 to 5; T₁, T₂, T₃, T₄and T₅ each independently represent a hydrogen atom or —OC_(p)H_(p+1);and p represents an integer of 1 to 5.

Each of the aliphatic hydrocarbon group having 1 to 12 carbon atoms, thehalogen-substituted alkyl group having 1 to 12 carbon atoms, thealicyclic hydrocarbon group having 3 to 14 carbon atoms, the aromatichydrocarbon group having 6 to 14 carbon atoms, and the heterocyclicgroup having 3 to 14 carbon atoms, each of which optionally has thegroup(s) L, preferably has a total of 50 or less carbon atoms, morepreferably 40 or less carbon atoms, particularly preferably 30 or lesscarbon atoms, including substituent(s). When the number of carbon atomsfalls within this range, the cyanine compound is more easilysynthesized, while absorption intensity per unit weight tends to behigh.

Examples of the aliphatic hydrocarbon group having 1 to 12 carbon atoms,the halogen-substituted alkyl group having 1 to 12 carbon atoms, thealicyclic hydrocarbon group having 3 to 14 carbon atoms, the aromatichydrocarbon group having 6 to 14 carbon atoms, the heterocyclic grouphaving 3 to 14 carbon atoms, and the group(s) L include the same asthose listed above, so that the description will be omitted here.

Examples of —S-L² include a thiol group, a methyl sulfide group, anethyl sulfide group, a propyl sulfide group, a butyl sulfide group, anisobutyl sulfide group, a sec-butyl sulfide group, a tert-butyl sulfidegroup, a phenyl sulfide group, a 2,6-di-tert-butylphenyl sulfide group,a 2,6-diphenylphenyl sulfide group, and a 4-cumylphenyl sulfide group.

Examples of —SS-L² include a disulfide group, a methyl disulfide group,an ethyl disulfide group, a propyl disulfide group, a butyl disulfidegroup, an isobutyl disulfide group, a sec-butyl disulfide group, atert-butyl disulfide group, a phenyl disulfide group, a2,6-di-tert-butylphenyl disulfide group, a 2,6-diphenylphenyl disulfidegroup, and a 4-cumylphenyl disulfide group.

Examples of —SO₂-L³ include a sulfoxyl group, a mesyl group, anethylsulfonyl group, a n-butylsulfonyl group, and a p-toluenesulfonylgroup.

Examples of —N═N-L⁴ include a methylazo group, a phenylazo group, ap-methylphenylazo group, and a p-dimethylaminophenylazo group.

The anion in the cyanine compound of the present embodiment can beprepared in accordance with a method described in Examples mentionedlater or with reference to the method. The cation in the cyaninecompound of the present embodiment can be prepared by a heretofore knownmethod.

The cyanine compound of the present embodiment, particularly, by havingthe anion mentioned above, easily has a local maximum absorptionwavelength of more than 800 nm. This facilitates more selectivelyabsorbing an incident light (particularly, infrared light) of more than800 nm, while suppressing the absorption of visible light. This ispresumably because the anion mentioned above has a structure that easilynarrows an energy gap, though the factor is not limited thereto.Furthermore, the cyanine compound of the present embodiment,particularly, by having the anion mentioned above, easily exhibitshigher durability performance (e.g., light resistance and heatresistance). This is presumably because the anion mentioned above has amore stabilized molecular orbital and because, particularly, when R¹ toR⁴ are bulky, active oxygen or the like is inhibited from coming closeto a methine site which is susceptible spontaneous oxidation so that thedeterioration of the anion is suppressed, though the factor is notlimited thereto.

(Photoelectric Conversion Element)

The photoelectric conversion element of the present embodiment refers toan element that has a photoelectric conversion unit which generates acharge in response to the quantity of an incident light in the infraredregion (hereinafter, also referred to as an infrared photoelectricconversion unit), and outputs the generated charge to the outside of thephotoelectric conversion element through a condenser (also referred toas an accumulation unit) for charge accumulation, a transistor circuit(also referred to as a readout unit) for readout, and the like. In thiscontext, the infrared photoelectric conversion unit refers to a unithaving an organic infrared photoelectric conversion film disposedbetween a pair of opposed electrodes, and a light is incident on thephotoelectric conversion unit from above the electrodes. The organicinfrared photoelectric conversion film is a photosensitive thin filmcontaining a material that absorbs at least a portion of incident lightsin the infrared region (hereinafter, referred to as an “organic infraredabsorptive material”), and generates holes and electrons as a result oflight incidence.

(Organic Infrared Absorptive Material)

The organic infrared absorptive material according to the presentembodiment contains the cyanine compound mentioned above.

In the organic infrared absorptive material according to the presentembodiment, the local maximum absorption wavelength and the maximumabsorption wavelength of optical absorption spectra in the infraredregion are preferably 800 nm or more and 2500 nm or less. Specifically,an organic photoelectric conversion film in the form of a thin filmprepared from the organic infrared absorptive material has lightabsorption peaks that exhibit local maximum and maximum values in thewavelength range of 800 nm to 2500 nm. In this range, the absorptionratio of an infrared light absorption peak is preferably 50% or more.

The organic infrared absorptive material according to the presentembodiment preferably has no or minimum absorption in a wavelengthregion other than 800 nm to 2500 nm. However, the organic infraredabsorptive material according to the present embodiment exhibits a localmaximum absorption wavelength and a maximum absorption wavelength ofoptical absorption spectra in the infrared region of 800 nm or more and2500 nm or less, and can achieve the absorption of the wavelength in asolid-phase state when used in the photoelectric conversion element. Ingeneral, a photoelectric conversion material for use in photoelectricconversion elements can improve sensitivity as its molar extinctioncoefficient is higher. Therefore, a higher molar extinction coefficientis preferred.

The organic infrared absorptive material according to the presentembodiment may be composed of only the cyanine compound or may containan additional infrared absorptive substance known in the art. Examplesof such a compound include cyanine compounds other than the compounddescribed above, squarylium compounds, croconium compounds, immoniumcompounds, dithiolene compounds, bisdithiolene compounds, porphyrincompounds, phthalocyanine compounds, naphthalocyanine compounds, BODIPYcompounds, and quaterrylene diimide.

(Organic Infrared Photoelectric Conversion Film)

The organic infrared photoelectric conversion film for use in thephotoelectric conversion element of the present embodiment can beobtained, for example, by preparing the organic infrared absorptivematerial into a thin film, Examples of the method for forming theorganic infrared photoelectric conversion film according to the presentembodiment include general dry film formation methods and wet filmformation methods. Specific examples of such a formation method include:resistance heating vapor deposition, electron beam vapor deposition,sputtering, and molecular lamination methods which are vacuum processes;casting which is a solution process; coating methods such as spincoating, dip coating, blade coating, wire bar coating, and spraycoating; printing methods such as inkjet printing, screen printing,offset printing, and relief printing; and soft lithography approachessuch as microcontact printing methods. A combined method of a pluralityof these approaches may be adopted for the film formation of each layer.

For example, in the dry film formation, the cyanine compound of thepresent embodiment, and optionally, a compound appropriate for theapplication of the photoelectric conversion element are mixed to preparea composition, which can then be vapor-deposited onto an electrode or anorganic thin film layer mentioned later in vacuum to obtain an organicinfrared photoelectric conversion film. In the wet film formationmethod, the cyanine compound of the present embodiment, and optionally,a compound appropriate for the application of the photoelectricconversion element are mixed together with a solvent to prepare a liquidcomposition, with which an electrode or an organic thin film can then becoated or printed, followed by drying to obtain an organic infraredphotoelectric conversion film.

The thickness of the organic infrared photoelectric conversion filmprepared so as to contain the cyanine compound depends on the resistancevalue and/or charge mobility of each substance and thus cannot belimited. The thickness is usually 0.5 nm or more and 5000 nm or less,preferably 1 nm or more and 1000 nm or less, more preferably 5 nm ormore and 500 nm or less.

The organic infrared photoelectric conversion film according to thepresent embodiment may contain an organic material other than thecyanine compound and preferably contains a p-type and/or n-type organicsemiconductor because incident light energy can be more efficientlyconverted to electric signals. Among others, an organic p-typesemiconductor that easily donates electrons (which has a smallionization potential) to the organic infrared absorptive material, or anorganic n-type semiconductor that easily accepts electrons therefrom(which has large electron affinity) is preferred because incident lightenergy can be still more efficiently converted to electric signals. Morespecifically, the ionization potential (HOMO level) is preferably −5.5eV or more in terms of a thin-film solid. The electron affinity (LUMOlevel) is preferably −3.0 eV or less in terms of a thin-film solid. Inthis context, the ionization potential (HOMO level) refers to a valuemeasured by photoemission yield spectroscopy in air. The electronaffinity (LUMO level) refers to a value determined by calculating anenergy band gap value from the absorption end of the longest wavelengthof near-infrared spectra, and subtracting the value from the HOMO level.

In the case of using an organic semiconductor, a form in which thecyanine compound of the present embodiment and the organic semiconductorare used as a mixture, and a multilayer form in which a layer preparedfrom only the cyanine compound of the present embodiment (hereinafter,referred to as a “cyanine compound layer”) and a layer prepared fromonly the organic semiconductor (hereinafter, referred to as an “organicsemiconductor layer”) are used may both be adopted.

In the case of using an organic semiconductor layer, the layer may beone layer or may be two or more layers. The organic semiconductor layermay be an organic p-type semiconductor film, may be an organic n-typesemiconductor film, or may be a mixed film thereof (bulk-heterostructure). Particularly, the organic semiconductor layer preferably hasa layer having a bulk-hetero junction structure. In such a case, theorganic infrared photoelectric conversion film is allowed to have abulk-hetero junction structure. This can compensate for thedisadvantage, i.e., a short carrier diffusion length, of the organicinfrared photoelectric conversion film and improve photoelectricconversion efficiency.

In the case of using the cyanine compound layer and the organicsemiconductor layer in combination, the thickness of a laminate of theselayers depends on the resistance value and/or charge mobility of eachsubstance and thus cannot be limited. The thickness is usually 0.5 nm ormore and 5000 nm or less, preferably 1 nm or more and 1000 nm or less,more preferably in the range of 5 to 500 nm. In this case, the organicsemiconductor layer is preferably on the order of two or more layers and10 or less layers.

Hereinafter, the organic semiconductor will be described in detail.

(Organic p-Type Semiconductor)

The organic p-type semiconductor (compound) is a donor organicsemiconductor (hereinafter, also referred to as a “donor organiccompound”) and refers to an organic compound that is typified mainly bya hole-transporting organic compound and has a property of easilydonating electrons. Further specifically, this compound refers to anorganic compound having a smaller ionization potential when two organicmaterials are used in contact. Thus, any organic compound may be used asthe donor organic compound as long as the organic compound haselectron-donating properties.

Examples of such a donor organic compound include triarylaminecompounds, benzidine compounds, pyrazoline compounds, styrylaminecompounds, hydrazone compounds, triphenylmethane compounds, carbazolecompounds, polysilane compounds, thiophene compounds, phthalocyaninecompounds, cyanine compounds, merocyanine compounds, oxonol compounds,polyamine compounds, indole compounds, pyrrole compounds, pyrazolecompounds, polyarylene compounds, condensed aromatic carbocycliccompounds (naphthalene derivatives, anthracene derivatives, phenanthrenederivatives, tetracene derivatives, pyrene derivatives, perylenederivatives, and fluoranthene derivatives), and metal complexes havingnitrogen-containing heterocyclic compounds as ligands. The donor organiccompound is not limited thereto, and as described above, an organiccompound having a smaller ionization potential than that of an organiccompound used as an acceptor organic compound may be used as the donororganic semiconductor.

(Organic n-Type Semiconductor)

The organic n-type semiconductor (compound) is an acceptor organicsemiconductor (hereinafter, also referred to as an “acceptor organiccompound”) and refers to an organic compound that is typified mainly byan electron-transporting organic compound and has a property of easilyaccepting electrons. Further specifically, this compound refers to anorganic compound having larger electron affinity when two organiccompounds are used in contact. Thus, any organic compound may be used asthe acceptor organic compound as long as the organic compound haselectron-accepting properties.

Examples of such an acceptor organic compound include condensed aromaticcarbocyclic compounds (naphthalene derivatives, anthracene derivatives,phenanthrene derivatives, tetracene derivatives, pyrene derivatives,perylene derivatives, fluoranthene derivatives, and fullerenederivatives), 5- to 7-membered heterocyclic compounds containing anitrogen atom, an oxygen atom, or a sulfur atom (e.g., pyridine,pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline,quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine,phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazole,oxazole, indazole, benzimidazole, benzotriazole, benzoxazole,benzothiazole, carbazole, purine, triazolopyridazine,triazolopyrimidine, tetrazaindene, oxadiazole, imidazopyridine,pyralidine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, andtribenzazepine), polyarylene compounds, fluorene compounds,cyclopentadiene compounds, silyl compounds, and metal complexes havingnitrogen-containing heterocyclic compounds as ligands. The acceptororganic compound is not limited thereto, and as described above, anorganic compound having larger electron affinity than that of an organiccompound used as a donor organic compound may be used as the acceptororganic semiconductor.

(Infrared Photoelectric Conversion Unit)

The infrared photoelectric conversion unit according to the presentembodiment has a pair of electrodes and the organic infraredphotoelectric conversion film disposed between the pair of electrodes.This infrared photoelectric conversion unit may employ an organic thinfilm layer in addition to the pair of electrodes and the organicinfrared photoelectric conversion film. This infrared photoelectricconversion unit may have, for example, an electron transport layer, ahole transport layer, an electron blocking layer, a hole blocking layer,an electron injection layer, a hole injection layer, a crystallizationprevention layer, and/or an interlayer contact improvement layer, as alayer other than the organic infrared photoelectric conversion film.Particularly, the infrared photoelectric conversion unit having one ormore selected from the group consisting of an electron transport layer,a hole transport layer, an electron blocking layer and a hole blockinglayer is preferred because the resulting element more efficientlyconverts even weak light energy to electric signals.

FIG. 1 is a cross-sectional schematic view partially showing one exampleof the infrared photoelectric conversion unit according to the presentembodiment. An infrared photoelectric conversion unit 100 shown in FIG.1 has an organic infrared photoelectric conversion film 110 containingan organic infrared absorptive material, a hole transport layer 120 andan electron transport layer 130 laminated so as to flank the organicinfrared photoelectric conversion film 110, and electrodes 140 and 150laminated so as to further flank the resultant. This infraredphotoelectric conversion unit 100 can selectively cause photoelectricconversion of an infrared wavelength of 800 nm or more among incidentlights including visible light and infrared light, principally due tothe organic infrared photoelectric conversion film containing an organicinfrared absorptive material. Hereinafter, each member possessed by theinfrared photoelectric conversion unit 100 will be described in detail.

(Electrode)

When the organic infrared photoelectric conversion film contained in theinfrared photoelectric conversion unit has hole-transporting propertiesor when an organic thin film layer other than the organic infraredphotoelectric conversion film is a hole transport layer havinghole-transporting properties, the electrode plays a role in extractingholes from the organic infrared photoelectric conversion film or theadditional organic thin film layer and collecting the holes. When theorganic infrared photoelectric conversion film contained in the infraredphotoelectric conversion unit has electron-transporting properties orwhen an organic thin film layer other than the organic infraredphotoelectric conversion film is an electron transport layer havingelectron-transporting properties, the electrode plays a role inextracting electrons from the organic infrared photoelectric conversionfilm or the additional organic thin film layer and discharging theelectrons.

The material that may be used in the electrode is not particularlylimited as long as it has conductivity to some extent. The material ispreferably selected in consideration of close contact with the adjacentorganic infrared photoelectric conversion film or additional organicthin film layer, electron affinity, an ionization potential andstability, etc. Examples of the material that may be used in theelectrode include: conductive metal oxides such as tin oxide (NESA),indium oxide, indium tin oxide (ITO) and indium zinc oxide (IZO); metalssuch as gold, silver, platinum, chromium, aluminum, iron, cobalt, nickeland tungsten: inorganic conductive substances such as copper iodide andcopper sulfide; conductive polymers such as polythiophene, polypyrroleand polyaniline; and carbon. These materials may each be used singly,may be used as a mixture of two or more thereof, or may be used as atwo-layer or more laminate of two or more thereof. The thickness of theelectrode can be arbitrarily selected in consideration of conductivity.The thickness may be 5 nm or more and 500 nm or less and is preferably10 nm or more and 300 nm or less.

The conductivity of the material for use in the electrode is notparticularly limited as long as it does not hinder the light receptionof the photoelectric conversion element more than necessary. Theconductivity is preferably as high as possible from the viewpoint of thesignal intensity and power consumption of the photoelectric conversionelement. For example, as for a transparent electrode, an ITO film havingconductivity equal to or less than a sheet resistance value of 300 ohmsper square sufficiently functions as the electrode. However, acommercially available product of a substrate having an ITO film havingconductivity on the order of several ohms per square (e.g., 5 to 9 ohmsper square) is also obtainable, and such a substrate having highconductivity is desirable.

In the case of using an ITO film, the thickness of the electrode can bearbitrarily selected in consideration of conductivity and is usually 5nm or more and 3000 nm or less, preferably 10 nm or more and 300 nm orless. Examples of the method for forming the film such as ITO includevapor deposition methods, electron beam methods, sputtering methods,chemical reaction methods and coating methods heretofore known in theart. The ITO film disposed on the substrate may be subjected, ifnecessary, to UV-ozone treatment or plasma treatment.

In the case of laminating a plurality of organic infrared photoelectricconversion films differing in wavelength to be detected, the film of anelectrode (which is the film of an electrode other than the pair ofelectrodes described above) for use between the respective organicinfrared photoelectric conversion films needs to be transmissive to alight having a wavelength other than the lights to be detected by therespective organic infrared photoelectric conversion films. From such aviewpoint, a material transmissive to 90% more of an incident light ispreferably used in the film of the electrode, and a materialtransmissive to 95% or more of a light is more preferably used.

In the case of further establishing a photoelectric conversion unit thatsenses a light in the visible light region beneath the infraredphotoelectric conversion unit according to the present embodiment, theelectrode for use in the infrared photoelectric conversion unitpreferably has a transmittance of 90% or more, more preferably 95% ormore, to visible light and infrared light.

The material for the electrode that satisfies such conditions ispreferably transparent conducting oxide (TCO) having a hightransmittance to visible light and infrared light and a small resistancevalue. Although a thin film of a metal such as Au can be used as anelectrode, its resistance value is extremely increased if thetransmittance is adjusted to 90% or more. Thus, TCO is preferred for theelectrode. The TCO is particularly preferably ITO, IZO, AZO, FTO, SnO₂,TiO₂ or ZnO₂.

The method for forming the electrode is not particularly limited and canbe appropriately selected in consideration of aptitude for the electrodematerial. In the case of using a transparent electrode, specificexamples of the formation method therefor include wet schemes such asprinting schemes and coating schemes, physical schemes such as vacuumvapor deposition methods, sputtering methods and ion plating methods,and chemical schemes such as CVD and plasma CVD. When the electrodematerial is transparent conducting metal oxide such as ITO, examples ofthe formation method therefor include electron beam methods, sputteringmethods, resistance heating vapor deposition methods, chemical reactionmethods (sol-gel methods, etc.), and methods of coating with adispersion of the metal oxide. The film of transparent conducting metaloxide such as ITO may be further subjected to UV-ozone treatment andplasma treatment.

Next, the organic thin film layer other than the organic infraredphotoelectric conversion film will be described.

The electron transport layer plays a role in transporting electronsgenerated in the organic infrared photoelectric conversion film to theelectrode, and a role in blocking hole migration to the organic infraredphotoelectric conversion film from the electrode to which electrons aretransported.

The hole transport layer plays a role in transporting generated holesfrom the organic infrared photoelectric conversion film to theelectrode, and a role in blocking electron migration to the organicinfrared photoelectric conversion film from the electrode to which holesare transported.

The electron blocking layer plays a role in blocking electron migrationfrom the electrode to the organic infrared photoelectric conversionfilm, preventing electron recombination in the organic infraredphotoelectric conversion film, reducing dark current, reducing noise,and expanding a dynamic range.

The hole blocking layer plays a role in blocking hole migration from theelectrode to the organic infrared photoelectric conversion film,preventing hole recombination in the organic infrared photoelectricconversion film, reducing dark current, reducing noise, and expanding adynamic range.

(Hole Transport Layer)

The material for the hole transport layer is not particularly limited aslong as it is known as a hole transport layer for photoelectricconversion elements such as solid image sensors. Examples thereofinclude polyaniline and doped materials thereof, and cyanogen compoundsdescribed in International Publication No. WO 2006/019270.

More specific examples of the material constituting the hole transportlayer include selenium, iodides such as copper iodide (CuI), cobaltcomplexes such as layered cobalt oxide, CuSCN, molybdenum oxide (MoO₃,etc.), nickel oxide (NiO, etc.), 4CuBr·3S(C₄H₉) and organic holetransport materials. Among them, examples of the iodide include copperiodide (CuI). Examples of the layered cobalt oxide include AxCoO₂(wherein A represents Li, Na, K, Ca, Sr or Ba, and 0≤X≤1).

Examples of the organic hole transport material include polythiophenederivatives such as poly-3-hexylthiophene (P3HT) andpoly(3,4-ethylenedioxythiophene) (PEDOT; e.g., trade name “BaytronP”manufactured by H.C. Starck-V Tech Ltd.), fluorene derivatives such as2,2′, 7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene(spiro-MeO-TAD), carbazole derivatives such as polyvinylcarbazole,triphenylamine derivatives, diphenylamine derivatives, polysilanederivatives, and polyaniline derivatives. Further examples of thematerial for the hole transport layer include compound semiconductorshaving monovalent copper, such as CuInSe₂ and copper sulfide (CuS),gallium phosphide (GaP), nickel oxide (NiO), cobalt oxide (CoO), ironoxide (FeO), bismuth oxide (Bi₂O₃), molybdenum oxide (MoO₂), andchromium oxide (Cr₂O₃).

The hole transport layer having a shallower LUMO level than that of theorganic infrared photoelectric conversion film is preferred because anelectron blocking function having a rectifying effect of suppressing themigration of electrons generated in the organic infrared photoelectricconversion film to the electrode side is imparted thereto. Such a holetransport layer is also called an electron blocking layer.

Examples of the low-molecular organic compound as the materialconstituting the electron blocking layer include aromatic diaminecompounds such as N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine(TPD) and 4,4′-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (α-NPD),oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbenederivatives, pyrazoline derivatives, tetrahydroimidazole,polyarylalkane, butadiene,4,4′,4″-tris(N-(3-methylphenyl)N-phenylamino)triphenylamine (m-MTDATA),porphyrin compounds such as porphyrin, copper tetraphenylporphyrin,phthalocyanine, copper phthalocyanine and titanium phthalocyanine oxide,triazole derivatives, oxadiazole derivatives, imidazole derivatives,polyarylalkane derivatives, pyrazoline derivatives, pyrazolonederivatives, phenylenediamine derivatives, arylamine derivatives,amino-substituted chalcone derivatives, oxazole derivatives,styrylanthracene derivatives, fluorenone derivatives, hydrazonederivatives, and silazanes derivatives. Examples of the high-molecularorganic compound include polymers such as phenylene vinylene, fluorene,carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene anddiacetylene, and derivatives thereof. A compound having sufficienthole-transporting properties, albeit being not an electron-donatingcompound, may be used as the material constituting the electron blockinglayer. Examples of the inorganic compound as the material constitutingthe electron blocking layer include metal oxides such as calcium oxide,chromium oxide, copper chromium oxide, manganese oxide, cobalt oxide,nickel oxide, copper oxide, copper gallium oxide, copper strontiumoxide, niobium oxide, molybdenum oxide, copper indium oxide, silverindium oxide and iridium oxide, selenium, tellurium and antimonysulfide. These materials may each be used singly or in combination oftwo or more thereof.

The thickness of the hole transport layer is preferably 10 nm or moreand 300 nm or less, more preferably 30 nm or more and 250 nm or less,further preferably 50 nm or more and 200 nm or less, from the viewpointof suppressing dark current, and preventing reduction in photoelectricconversion efficiency.

The method for forming the hole transport layer may be a heretoforeknown method and may be any of dry film formation methods such as vacuumvapor deposition methods, and wet film formation methods such assolution coating methods. A wet film formation method is preferred fromthe viewpoint of being able to level a coated surface. Examples of thedry film formation method include vapor deposition methods such asvacuum vapor deposition methods, and sputter methods. The vapordeposition may be any of physical vapor deposition (PVD) and chemicalvapor deposition (CVD) and is preferably physical vapor deposition suchas vacuum vapor deposition. Examples of the wet film formation methodinclude inkjet methods, spray methods, nozzle print methods, spincoating methods, dip coating methods, casting methods, die coatingmethods, roll coating methods, bar coating methods and gravure coatingmethods.

(Electron Transport Layer)

The material constituting the electron transport layer is notparticularly limited as long as it is known as an electron transportlayer for photoelectric conversion elements such as solid image sensors.Examples thereof include organic compounds such as perfluoro forms(perfluoropentacene, perfluorophthalocyanine, etc.) of octaazaporphyrinand p-type semiconductors, fullerene, fullerene derivatives (e.g.,[6,6]-phenyl-C61-butyric acid methyl ester; PCBM), perylene,indenoindene and indenoindene derivatives, and inorganic oxides such astitanium oxide (TiO₂, etc.), nickel oxide (NiO), tin oxide (SnO₂),tungsten oxide (WO₂, WO₃, W₂O₃, etc.), zinc oxide (ZnO), niobium oxide(Nb₂O₅, etc.), tantalum oxide (Ta₂O₅, etc.), yttrium oxide (Y₂O₃, etc.),and strontium titanate (SrTiO₃, etc.). The electron transport layer maybe a porous layer or may be a dense layer. In the case of laminatingthem, the porous electron transport layer and the dense electrontransport layer are preferably laminated and disposed in this order fromthe organic infrared photoelectric conversion film side.

The electron transport layer having a deeper HOMO level than that of theorganic infrared photoelectric conversion film is preferred because ahole blocking function having a rectifying effect of suppressing themigration of holes generated in the organic infrared photoelectricconversion film to the opposite electrode side is imparted thereto. Suchan electron transport layer is also called a hole blocking layer.

Examples of the material constituting the hole blocking layer includeoxadiazole derivatives such as1,3-bis(4-tert-butylphenyl-1,3,4-oxadiazolyl)phenylene (OXD-7),anthraquinone dimethane derivatives, diphenylquinone derivatives,bathocuproine, bathophenanthroline, and their derivatives, triazolecompounds, tris(8-hydroxyquinolinato)aluminum complexes,bis(4-methyl-8-quinolinato)aluminum complexes, silole compounds,porphyrin compounds, styryl compounds such as DCM(4-dicyanomethylene-2-methyl-6-(4-(dimethylaminostyryl))-4H-pyran),n-type semiconductor materials such as naphthalenetetracarboxylicanhydrides, naphthalenetetracarboxylic acid diimide,perylenetetracarboxylic anhydrides, and perylenetetracarboxylic aciddiimide, n-type inorganic oxides such as titanium oxide, zinc oxide andgallium oxide, and alkali metal fluorides such as lithium fluoride,sodium fluoride and cesium fluoride. Further, an alkali metal compounddoped with an organic semiconductor molecule is also preferred becauseof having a function of improving electric junction to the oppositeelectrode. These materials may each be used singly or in combination oftwo or more thereof.

The thickness of the electron transport layer is preferably 10 nm ormore and 300 nm or less, more preferably 30 nm or more and 250 nm orless, further preferably 50 nm or more and 200 nm or less, from theviewpoint of suppressing dark current, and preventing reduction inphotoelectric conversion efficiency.

The method for forming the electron transport layer may be a heretoforeknown method and may be any of dry film formation methods such as vacuumvapor deposition methods, and wet film formation methods such assolution coating methods. A wet film formation method is preferred fromthe viewpoint of being able to level a coated surface. Examples of thedry film formation method include vapor deposition methods such asvacuum vapor deposition methods, and sputter methods. The vapordeposition may be any of physical vapor deposition (PVD) and chemicalvapor deposition (CVD) and is preferably physical vapor deposition suchas vacuum vapor deposition. Examples of the wet film formation methodinclude inkjet methods, spray methods, nozzle print methods, spincoating methods, dip coating methods, casting methods, die coatingmethods, roll coating methods, bar coating methods and gravure coatingmethods.

(Interlayer Contact Improvement Layer)

The interlayer contact improvement layer has a function of reducingdamage on a lower film nearest to an upper electrode, for example, theorganic infrared photoelectric conversion film, at the time of filmformation of the upper electrode. Particularly, high-energy particlespresent in an apparatus for use in the film formation of the upperelectrode to be formed, for example, sputter particles, secondaryelectrons, Ar particles, or oxygen anions in a sputtering method, maydeteriorate the lower film nearest thereto through collision, resultingin performance deterioration such as increased leak current or reducedsensitivity. One of the methods for preventing this preferably involvesestablishing an interlayer contact improvement layer on an upper layerof the nearest lower film. An organic material such as copperphthalocyanine, PTCDA, an acetyl acetonate complex, or BCP, an organicmetal compound, or an inorganic material such as MgAg or MgO ispreferably used as the material for the interlayer contact improvementlayer. The thickness of the interlayer contact improvement layer differsin proper range depending on the configuration of a photoelectricconversion film, the film thickness of an electrode, etc. It isparticularly preferred to select a material having no absorption in thevisible region, or the thickness is preferably 2 nm or more and 50 nmfrom the viewpoint of using a very small thickness.

The photoelectric conversion element of the present embodiment has aninfrared photoelectric conversion unit that generates a charge inresponse to the quantity of an incident light in the infrared region.The generated charge is read out as signals depending on the quantity ofthe charge by a semiconductor. Hence, the photoelectric conversionelement is connected with a condenser for accumulation of the generatedcharge (hereinafter, also referred to as an “accumulation unit”) and atransistor circuit for readout (hereinafter, also referred to as a“readout unit”) via a connection unit made of a conductive material.Also, the photoelectric conversion element optionally contains asubstrate for strength retention, a microlens for light collection, orthe like.

(Accumulation Unit, Readout Unit, and Connection Unit)

The readout unit is disposed in order to read out signals depending on acharge generated in the organic infrared photoelectric conversion film.The readout unit is constituted by, for example, CCD, a CMOS circuit, ora TFT circuit, and preferably shielded from lights by a light shieldinglayer disposed in an insulating layer. The readout circuit iselectrically connected with its corresponding electrode via a connectionunit. In order to secure a charge in a quantity necessary for readout,an accumulation unit constituted by a condenser or the like mayintervene between the electrode and the connection unit. The connectionunit is embedded in the insulating layer and is a plug or the like forelectrically connecting the electrode (e.g., a transparent electrode oran opposite electrode) to the readout unit. When the member thusconfigured is a solid image sensor, upon light incidence, the light isincident on the organic infrared photoelectric conversion film where acharge is then generated. Electrons in the generated charge arecollected (and accumulated) in one electrode, and voltage signalsdepending on the quantity thereof is output to the outside of the solidimage sensor by the readout unit.

(Visible Photoelectric Conversion Unit)

The photoelectric conversion element of the present embodimentpreferably has a visible photoelectric conversion unit having absorptionspectra in the visible light region, from the viewpoint of improvingphotoelectric conversion sensitivity, and from the viewpoint ofimproving an image processing rate when infrared imaging or positionalinformation using infrared light is used in combination with visibleimaging. This visible photoelectric conversion unit can be disposedbeneath the infrared photoelectric conversion unit in order tosimultaneously sense visible light and infrared light by thephotoelectric conversion of a transmitted light in the visible lightregion when the infrared photoelectric conversion unit is transmissiveto a light in the visible region, for example, when the photoelectricconversion element of the present embodiment has a transparentelectrode.

The visible photoelectric conversion unit may sense a light in thevisible light region by using a heretofore known silicon photodiode or adevice having an organic photoelectric conversion material sensitive tovisible light (e.g., those described in Japanese Patent ApplicationLaid-Open No. 2013-258168). For color imaging, a color filter or thelike may be disposed above the visible photoelectric conversion unit, orthe visible photoelectric conversion unit may be laminated with anorganic photoelectric conversion layer differing in visible lightwavelength sensitivity therefrom.

The photoelectric conversion element of the present embodiment,particularly, by having the organic infrared photoelectric conversionfilm containing the cyanine compound having the anion mentioned above,is facilitated to more selectively absorb an incident light(particularly, infrared light) of more than 800 nm, and is consequentlyexcellent in photoelectric conversion efficiency. This is presumablybecause the anion mentioned above has a structure that easily narrows anenergy gap, though the factor is not limited thereto. Furthermore, thephotoelectric conversion element of the present embodiment,particularly, by having the organic infrared photoelectric conversionfilm containing the cyanine compound having the anion mentioned above,easily exhibits higher durability performance (e.g., light resistanceand heat resistance). This is presumably because the anion mentionedabove has a more stabilized molecular orbital, though the factor is notlimited thereto.

(Solid Image Sensor)

The solid image sensor of the present embodiment has a large number ofphotoelectric conversion elements of the present embodiment disposed inan array pattern. Specifically, a large number of photoelectricconversion elements disposed in an array pattern constitute a solidimage sensor that exhibits the quantity of an incident light as well aspositional information on incidence.

In the solid image sensor, a plurality of photoelectric conversion unitsmay be laminated as long as an infrared photoelectric conversion unitdisposed nearer a light source does not block (or is transmissive to)the absorption wavelength of another photoelectric conversion unit(visible photoelectric conversion unit, etc.) disposed at the backthereof viewed from the light source side.

In the solid image sensor, the infrared photoelectric conversion unit orthe visible photoelectric conversion unit may be partially constitutedas a thin film in the same plane having no structural separation betweenthe adjacent photoelectric conversion elements, from the viewpoint ofeasy molding.

The solid image sensor of the present embodiment may further include asubstrate. The substrate is used for producing the solid image sensor bylaminating each layer thereon, or used for enhancing the mechanicalstrength of the solid image sensor. Examples of the type of thesubstrate include, but are not particularly limited to, semiconductorsubstrates, glass substrates and plastic substrates.

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to Examples. However, the present invention is not limited bythese Examples.

Example 1

First, compound 1a was synthesized in accordance with the followingscheme.

To a solution of an isopropyl magnesium chloride-lithium chloridecomplex in dry tetrahydrofuran (approximately 14%),bromopentafluorobenzene was added such that the molar ratio between thecomplex and the bromopentafluorobenzene was 1.05:1.00. The mixture wasreacted by stirring at −78° C. for 45 minutes. To the obtained product,2,3-butanedione was added such that the molar ratio between the productand the 2,3-butanedione was 1.0:1.1. The mixture was reacted by stirringat room temperature for 2.5 hours to obtain compound 1a. The obtainedcompound 1a was purified, and its yield was measured and wasconsequently 53%.

Next, tricyanofuran fluoride 2 a was synthesized in accordance with thefollowing scheme. The tricyanofuran fluoride 2 a was synthesized withreference to Chem, Mater. 2002, 14, p. 2393-2400.

A 1 M ethanol solution supplemented with 5 mol % of lithium ethoxide,and malononitrile were added to dry tetrahydrofuran, and further, thecompound 1a was added thereto such that the molar ratio between themalononitrile and the compound 1a was 2:1. The mixture was reacted byreflux overnight to obtain tricyanofuran fluoride 2 a. The obtainedtricyanofuran fluoride 2 a was purified, and its yield was measured andwas consequently 10%.

Also, dialdehyde 3 known in the art was synthesized in accordance withthe following scheme.

Excess dimethylformamide and 4 equivalents of phosphoryl chloride basedon cyclohexanone were mixed and reacted at 0° C. for 30 minutes. To theobtained product, cyclohexanone was added, and the mixture was furtherreacted by stirring at 55° C. for 3.5 hours to obtain dialdehyde 3. Theobtained dialdehyde 3 was purified, and its yield was measured and wasconsequently 52%.

Further, cyanine compound 4a having a perfluorophenyl group wassynthesized in accordance with the following scheme.

The dialdehyde 3 and the tricyanofuran fluoride 2 a were added intoacetic anhydride supplemented with sodium acetate such that the molarratio among the dialdehyde 3, the tricyanofuran fluoride 2 a, and thesodium acetate was 1.0:2.1:2.2. The mixture was reacted by stirring at120° C. for 4 hours to synthesize cyanine compound 4a. The obtainedcyanine compound 4a was purified, and its yield was measured and wasconsequently 40%. Results of NMR measurement (measurement apparatusproduct name: JTM-ECS400, manufactured by JEOL Ltd.; the same holds truefor the description below) thereof are shown below.

¹H NMR (Acetone-d₆) δ 1.70-1.76 (m, 2H, —CH₂CH₂CH₂—), 2.16-2.19 (m, 6H,—CH₃ X 2), 2.41-2.56 (m, 4H, —CH₂CH₂CH₂—), 6.14 (d, J=14.2 Hz, 2H, vinylH), 7.54 (d, J=14.2 Hz, 1H, vinyl H), 7.62 (d, J=14.2 Hz, 1H, vinyl H),¹⁶F NMR (Acetone-d₆) δ −162.8 (q, J=17.3 Hz, 2F), −153.1 (dt, J=53.5,21.0 Hz, 1F), −139.3 (d, J=20.2 Hz. 2F).

Example 2

Cyanine compound 5a having a perfluorophenyl group was synthesized inaccordance with the following scheme.

The cyanine compound 4a obtained in Example 1 was added into an acetonesolution supplemented with tetrabutylammonium iodide such that the molarratio between the cyanine compound 4a and the tetrabutylammonium iodidewas 1.0:1.1. The mixture was reacted by stirring at room temperature for1 hour to synthesize cyanine compound 5a. The obtained cyanine compound5a was purified, and its yield was measured and was consequently 69%.Results of NMR measurement thereof are shown below.

¹H NMR (Acetone-d₆) δ 0.95 (t, J=7.3 Hz, 12H, —CH₂CH₂CH₂CH₃ X 4),1.36-1.46 (m, 8H, —CH₂CH₂CH₂CH₃ X 4), 1.67-1.73 (m, 2H, —CH₂CH₂CH₂—),1.76-1.84 (m, 8H, —CH₂CH₂CH₂CH₃ X 4), 2.13-2.17 (m, 6H, —CH₃ X 2),2.42-2.54 (m, 4H, —CH₂CH₂CH₂—), 3.39-3.44 (m, 8H, —CH₂CH₂CH₂CH₃ X 4),6.11 (d, J=14.7 Hz, 2H, vinyl H), 7.53 (d, J=14.7 Hz, 1H, vinyl H), 7.66(d, J=14.7 Hz, 1H, vinyl H), ¹⁹F NMR (Acetone-d₆) δ −162.8 (q, J=16.9Hz, 2F), −153.1 (dt, J=50.0, 20.2 Hz, 1F), −139.3 (d, J=18.8 Hz, 2F).

Reference Example 1

Compound 1b known in the art was synthesized in accordance with thefollowing scheme. The compound 1b was synthesized with reference toAngew. Chem, Int. Ed., 2017, 56, p. 2478-2481.

To a solution of phenyl magnesium bromide in dry tetrahydrofuran,2,3-butanedione was added at 0° C. such that the molar ratio between thephenyl magnesium bromide and the 2,3-butanedione was 1.05:1.00. Then,the mixture was reacted by stirring at room temperature for 3 hours toobtain compound 1b. The crude yield of the obtained compound 1b wasmeasured and was consequently 87%.

Next, tricyanofuran 2b was synthesized in accordance with the followingscheme.

A 1 M ethanol solution supplemented with 5 mol % of lithium ethoxide,and malononitrile were added to dry tetrahydrofuran, and further, thecompound 1b obtained as described above was directly added theretowithout being purified such that the molar ratio between themalononitrile and the compound 1b was 2:1. The mixture was reacted byreflux overnight to obtain tricyanofuran 2b. The obtained tricyanofuran2b was purified, and its yield was measured and was consequently 25%.

Further, cyanine compound 4b was synthesized in accordance with thefollowing scheme.

The dialdehyde 3 and the tricyanofuran 2b were added into aceticanhydride supplemented with sodium acetate such that the molar ratioamong the dialdehyde 3, the tricyanofuran 2b, and the sodium acetate was1.0:2.1:2.2. The mixture was reacted by stirring at 120° C. for 4 hoursto synthesize cyanine compound 4b. The obtained cyanine compound 4b waspurified, and its yield was measured and was consequently 38%. Resultsof NMR measurement thereof are shown below.

¹H NMR (Acetone-d₆) δ 1.65-1.71 (m, 2H, —CH₂CH₂CH₂—), 2.08-2.09 (m, 6H,—CH₃ X 2), 2.35-2.46 (m, 4H, —CH₂CH₂CH₂—), 6.05 (d, J=14.2 Hz, 1H, vinylH), 6.07 (d, J=14.2 Hz, 1H, vinyl H), 7.38-7.47 (m, 6H, aryl H),7.50-7.52 (m, 4H, aryl H), 7.60 (d, J=14.2 Hz, 1H, vinyl H), 7.65 (d,J=14.2 Hz, 1H, vinyl H).

Reference Example 2

Cyanine compound 5b was synthesized in accordance with the followingscheme.

The cyanine compound 4b obtained in Reference Example 1 was added intoan acetone solution supplemented with tetrabutylammonium iodide suchthat the molar ratio between the cyanine compound 4b and thetetrabutylammonium iodide was 1.0:1.1. The mixture was reacted bystirring at room temperature for 1 hour to synthesize cyanine compound5b. The obtained cyanine compound 5b was purified, and its yield wasmeasured and was consequently 65%. Results of NMR measurement thereofare shown below.

¹H NMR (Acetone-d₆) δ 0.98 (t. J=7.3 Hz, 12H, —CH₂CH₂CH₂CH₃ X 4),1.39-1.48 (m, 8H, —CH₂CH₂CH₂CH₃ X 4), 1.67-1.73 (m, 2H, —CH₂CH₂CH₂—),1.80-1.87 (m, 8H, —CH₂CH₂CH₂CH₃ X 4), 2.10 (m, 6H, —CH₃ X 2), 2.38-2.48(m, 4H, —CH₂CH₂CH₂—), 3.43-3.47 (m, 8H, —CH₂CH₂CH₂CH₃ X 4), 6.05 (d,J=14.2 Hz, 1H, vinyl H), 6.07 (d, J=14.2 Hz, 1H, vinyl H), 7.39-7.48 (m,6H, aryl H), 7.51-7.53 (m, 4H, aryl H), 7.53 (d, J=14.2 Hz, 1H, vinylH), 7.66 (d, J=14.2 Hz, 1H, vinyl H).

Comparative Example 1

A compound represented by the following formula was synthesized by amethod known in the art.

The local maximum absorption in a dichloromethane solution (1×10⁻⁶ M) ofthe compound obtained in each of Example 2, Reference Example 2 andComparative Example 1, and the transmittance thereof in each wavelengthregion were measured using a spectrophotometer manufactured by HitachiHigh-Tech Corp. (product name: U-4100). As one example thereof, theabsorption spectra of the compound of Example 2 are shown in FIG. 2 . Inthe obtained absorption spectra, the local maximum absorption wavelengthwas 934 nm in Example 2, 920 nm in Reference Example 2, and 906 nm inComparative Example 1.

<Light Resistance>

In a thermostat bath of 25° C., a dehydrated dichloromethane solution(1×10⁻⁶ M) of the compound obtained in each of Example 2, ReferenceExample 2 and Comparative Example 1 was continuously irradiated with awhite LED light (L-711) to examine the residual ratio of the compound inthe solution (the concentration of the compound in the solutionimmediately before irradiation is defined as 100%). Thirteen days afterthe start of irradiation, the residual ratio of the compound of Example2 was 69%, whereas the residual ratio of the compound of ReferenceExample 2 was 45%. The residual ratio of the compound of ComparativeExample 1 fell below the detection limit 12 days after the start ofirradiation.

<Heat Resistance>

The decomposition temperature of the compound obtained in each ofExample 2, Reference Example 2 and Comparative Example 1 was measured byTG-DTA (apparatus name: EXSTAR-6000 TG/DTA 6300, manufactured by SeikoInstruments Inc.). The sample used in measurement was subjected to heatdrying treatment under reduced pressure (80° C., 3×10² Pa, overnight) inadvance. In the measurement, the temperature was elevated from 30° C. to400° C. in a nitrogen atmosphere, and the temperature at which theweight was decreased by 2% was measured. The temperature at which theweight of the compound of Example 2 was decreased by 2% wasapproximately 207° C., whereas the temperature at which the weight ofthe compound of Reference Example 2 was decreased by 2% wasapproximately 200° C. and the temperature at which the weight of thecompound of Comparative Example 1 was decreased by 2% was approximately198° C.

The present application is based on the Japanese patent applicationfiled on Sep. 25, 2020 (Japanese Patent Application No. 2020-161368),the contents of which are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The cyanine compound of the present invention has absorption ofnear-infrared light of more than 800 nm and has no or minimumsensitivity to visible light. The cyanine compound of the presentinvention is also excellent in durability performance such as lightresistance and heat resistance. Hence, the cyanine compound of thepresent invention can be used as a material for a photoelectricconversion element that has transparency, generates a charge in responseto near-infrared light, and is excellent in durability. Thus, thecyanine compound and the photoelectric conversion element of the presentinvention have industrial applicability in fields that require thesecharacteristics. Specifically, the cyanine compound and thephotoelectric conversion element of the present invention haveindustrial applicability as a solid image sensor in, for example, imagesensors for security cameras, in-car cameras, cameras for uninhabitedair vehicles, agricultural cameras, industrial cameras, medical camerassuch as endoscopic cameras, cameras for game machines, digital stillcameras, digital video cameras, cameras for mobile phones, and camerasfor the other mobile instruments; image scanning elements forfacsimiles, scanners and copying machines; and photosensors forbiosensors and chemical sensors. Also, the cyanine compound and thephotoelectric conversion element of the present invention haveindustrial applicability as a display in, for example, televisionmonitors, touch monitors, digital signages, wearable displays,electronic papers, and head-up displays for mobility application. Thecyanine compound of the present invention also has industrialapplication, for example, as a material for optical informationrecording media, flash fusing photosensitive materials, thermalshielding films, infrared cut filters, anti-counterfeit ink, or as apreform heating auxiliary agent intended for plastic bottles, inaddition to those mentioned above.

REFERENCE SIGNS LIST

100 . . . infrared photoelectric conversion unit, 110 . . . organicinfrared photoelectric conversion film, 120 . . . hole transport layer,130 . . . electron transport layer, 140, 150 . . . electrode.

1. A cyanine compound being bound counterions consisting of an anion anda cation, wherein the anion is represented by the following formula(I-1):

wherein R¹ and R² each independently represent a hydrogen atom or amonovalent organic group; R³ and R⁴ each independently represent amonovalent group represented by the following formula (I-1-1); Xrepresents a hydrogen atom, a halogen atom or a monovalent organicgroup; and Y represents a divalent group represented by the followingformula (I-1-2) or (I-1-3):

wherein R^(a), R^(b), R^(c), R^(d) and R^(e) each independentlyrepresent a hydrogen atom, a monovalent hydrocarbon group or amonovalent electron-withdrawing group; one or more of R^(a), R^(b),R^(c), R^(d) and R^(e) represent the monovalent electron-withdrawinggroup; and when one of R^(a), R^(b), R^(e), R^(d) and R^(e) is a halogenatom, one or more of the other moieties of R^(a), R^(b), R^(e), R^(d)and R^(e) represent the monovalent hydrocarbon group or the monovalentelectron-withdrawing group,

wherein R^(f), R^(g), R^(h), and R^(k) each independently represent ahydrogen atom, or a monovalent hydrocarbon group optionally havingoxygen atom(s), nitrogen atom(s) or sulfur atom(s), and

wherein R^(l), R^(m), R^(n) and R^(o) each independently represent ahydrogen atom, or a monovalent hydrocarbon group optionally havingoxygen atom(s), nitrogen atom(s) or sulfur atom(s).
 2. The cyaninecompound according to claim 1, wherein the cation comprises one or moreselected from the group consisting of an alkali metal cation, analkaline earth metal cation, an ammonium cation, a sulfonium cation, aphosphonium cation and cationic cyanine.
 3. The cyanine compoundaccording to claim 2, wherein the cation comprises one or more selectedfrom the group consisting of an alkali metal cation, an ammonium cationand cationic cyanine.
 4. The cyanine compound according to claim 3,wherein the cationic cyanine is a cation represented by the followingformula (I-2-1), (I-2-2), (I-2-3) or (I-2-4):

wherein each E independently represents a carbon atom, a nitrogen atom,an oxygen atom or a sulfur atom; R^(p), R^(q), R^(r), R^(s), R^(t),R^(u), R^(v), R^(w) and R^(x) each independently represent a hydrogenatom, a halogen atom, a hydroxy group, a carboxy group, a nitro group,an amino group, an amide group, an imide group, a cyano group, a silylgroup, -L¹, —S-L², —SS-L², —SO₂-L³, —N═N-L⁴, or one or more groupsselected from the group consisting of groups represented by thefollowing formulas (A), (B), (C), (D), (E), (F), (G) and (H) having oneor more combinations of R^(q) and R^(r), R^(s) and R^(t), R^(t) andR^(u), R^(u) and R^(v), R^(v) and R^(w), and R^(w) and R^(x) bonded toeach other, wherein the amino group, the amide group, the imide groupand the silyl group can be each further substituted by one or moregroups L selected from the group consisting of a monovalent aliphatichydrocarbon group having 1 to 12 carbon atoms, a monovalenthalogen-substituted alkyl group having 1 to 12 carbon atoms, amonovalent alicyclic hydrocarbon group having 3 to 14 carbon atoms, amonovalent aromatic hydrocarbon group having 6 to 14 carbon atoms and amonovalent heterocyclic group having 3 to 14 carbon atoms; each of theL¹ and the L⁴ is a monovalent aliphatic hydrocarbon group having 1 to 12carbon atoms, a monovalent halogen-substituted alkyl group having 1 to12 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms or a heterocyclic group having 3 to 14 carbon atoms, eachof which can be further substituted by the group(s) L; the L² is ahydrogen atom, or a monovalent aliphatic hydrocarbon group having 1 to12 carbon atoms, a monovalent halogen-substituted alkyl group having 1to 12 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to14 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms or a heterocyclic group having 3 to 14 carbon atoms, eachof which can be further substituted by the group(s) L; and the L³ is ahydroxy group, or a monovalent aliphatic hydrocarbon group having 1 to12 carbon atoms, a monovalent halogen-substituted alkyl group having 1to 12 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to14 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms or a heterocyclic group having 3 to 14 carbon atoms, eachof which can be further substituted by the group(s) L; Q¹ represents anacetyl group; and Q² represents a structure represented by the followingformula (q1), (q2) or (q3):

wherein the combination of R^(x) and R^(y) is a combination of R^(q) andR^(r), R^(s) and R^(t), R^(t) and R^(u), R^(u) and R^(v), R^(v) andR^(w), or R^(w) and R^(x); R_(A), R_(B), R_(C), R_(D), R_(E), R_(F),R_(G), R_(H), R_(I), R_(J), R_(K) and R_(L) each independently representa hydrogen atom, a halogen atom, a hydroxy group, a carboxy group, anitro group, an amino group, an amide group, an imide group, a cyanogroup, a silyl group, -L¹, —S-L², —SS-L², —SO₂-L³ or —N═N-L⁴, whereinL¹, L², L³ and L⁴ are as defined in L¹, L², L³ and L⁴ in the formulas(I-2-1) and (I-2-2), and the amino group, the amide group, the imidegroup and the silyl group can be substituted by the group(s) L,—C_(m)H_(m+1)  (q1)—C_(a)H_(a+1)—OC_(b)H_(b+1)  (q2) wherein m in the formula (q1)represents an integer of 1 to 5, and a and b in the formula (q2) eachrepresent an integer of 1 to 5, and

wherein n represents an integer of 1 to 5; T₁, T₂, T₃, T₄ and T₅ eachindependently represent a hydrogen atom or —OC_(p)H_(p+1); and prepresents an integer of 1 to
 5. 5. The cyanine compound according toclaim 1, wherein the monovalent organic group represented by each of theR¹ and the R² is a monovalent aliphatic hydrocarbon group having 1 to 12carbon atoms, a monovalent halogen-substituted alkyl group having 1 to12 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms or a heterocyclic group having 3 to 14 carbon atoms, eachof which can be further substituted by a monovalent hydrocarbon group ora monovalent electron-withdrawing group.
 6. The cyanine compoundaccording to claim 5, wherein the R¹ and the R² are each independently ahydrogen atom, a monovalent aliphatic hydrocarbon group having 1 to 3carbon atoms or a monovalent group represented by the formula (I-1-1).7. The cyanine compound according to claim 1, wherein the monovalentorganic group represented by the X represents a hydroxy group, a carboxygroup, a nitro group, an amino group, an amide group, an imide group, acyano group, a silyl group, -L¹, —S-L², —SS-L³, —SO₂-L³, or —N═N-L⁴,wherein the amino group, the amide group, the imide group and the silylgroup can be each further substituted by one or more groups L selectedfrom the group consisting of a monovalent aliphatic hydrocarbon grouphaving 1 to 12 carbon atoms, a monovalent halogen-substituted alkylgroup having 1 to 12 carbon atoms, a monovalent alicyclic hydrocarbongroup having 3 to 14 carbon atoms, a monovalent aromatic hydrocarbongroup having 6 to 14 carbon atoms and a monovalent heterocyclic grouphaving 3 to 14 carbon atoms; each of the L¹ and the L⁴ is a monovalentaliphatic hydrocarbon group having 1 to 12 carbon atoms, a monovalenthalogen-substituted alkyl group having 1 to 12 carbon atoms, amonovalent alicyclic hydrocarbon group having 3 to 14 carbon atoms, amonovalent aromatic hydrocarbon group having 6 to 14 carbon atoms or aheterocyclic group having 3 to 14 carbon atoms, each of which can befurther substituted by the group(s) L; the L² is a hydrogen atom, or amonovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms, amonovalent halogen-substituted alkyl group having 1 to 12 carbon atoms,a monovalent alicyclic hydrocarbon group having 3 to 14 carbon atoms, amonovalent aromatic hydrocarbon group having 6 to 14 carbon atoms or aheterocyclic group having 3 to 14 carbon atoms, each of which can befurther substituted by the group(s) L; and the L³ is a hydroxy group, ora monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms, amonovalent halogen-substituted alkyl group having 1 to 12 carbon atoms,a monovalent alicyclic hydrocarbon group having 3 to 14 carbon atoms, amonovalent aromatic hydrocarbon group having 6 to 14 carbon atoms or aheterocyclic group having 3 to 14 carbon atoms, each of which can befurther substituted by the group(s) L.
 8. The cyanine compound accordingto claim 7, wherein the X is a halogen atom.
 9. The cyanine compoundaccording to claim 1, wherein the monovalent hydrocarbon grouprepresented by each of the R^(a), the R^(b), the R^(c), the R^(d) andthe R^(e) is a monovalent aliphatic hydrocarbon group having 1 to 12carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms, each of which can be further substituted by one or moregroups selected from the group consisting of a monovalent aliphatichydrocarbon group having 1 to 12 carbon atoms, a monovalent alicyclichydrocarbon group having 3 to 14 carbon atoms and a monovalent aromatichydrocarbon group having 6 to 14 carbon atoms.
 10. The cyanine compoundaccording to claim 1, wherein the monovalent electron-withdrawing grouprepresented by each of the R^(a), the R^(b), the R^(c), the R^(d) andthe R^(e) is a halogen atom, a carboxy group, a nitro group, a cyanogroup, a group represented by —COR, a group represented by —CONR₂, agroup represented by —SO₂R or a group represented by —SO₃R, wherein theR is as defined in the monovalent hydrocarbon group or a hydrogen atom.11. The cyanine compound according to claim 10, wherein the R^(a), theR^(b), the R^(c), the R^(d) and the R^(e) each independently represent ahydrogen atom or a halogen atom, and two or more of R^(a), R^(b), R^(c),R^(d) and R^(e) are halogen atoms.
 12. The cyanine compound according toclaim 1, wherein the monovalent hydrocarbon group optionally havingoxygen atom(s), nitrogen atom(s) or sulfur atom(s), represented by eachof the R^(f), the R^(g), the R^(h), the R^(i), the R^(j), the R^(k), theR^(l), the R^(m), the R^(h) and the R^(o) is a monovalent aliphatichydrocarbon group having 1 to 12 carbon atoms, a monovalent alicyclichydrocarbon group having 3 to 14 carbon atoms or a monovalent aromatichydrocarbon group having 6 to 14 carbon atoms, each of which can befurther substituted by one or more groups selected from the groupconsisting of a monovalent aliphatic hydrocarbon group having 1 to 12carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 14carbon atoms and a monovalent aromatic hydrocarbon group having 6 to 14carbon atoms, each of which optionally has oxygen atom(s), nitrogenatom(s) or sulfur atom(s).
 13. The cyanine compound according to claim12, wherein R^(f), R^(g), R^(h), R^(i), R^(j), R^(k), R^(l), R^(m),R^(n) and R^(o) each independently represent a hydrogen atom, or amonovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms. 14.A photoelectric conversion element comprising an infrared photoelectricconversion unit comprising a pair of electrodes and an organic infraredphotoelectric conversion film disposed between the pair of electrodes,wherein the organic infrared photoelectric conversion film comprises thecyanine compound according to claim
 1. 15. The photoelectric conversionelement according to claim 14, wherein the organic infraredphotoelectric conversion film comprises an organic n-type semiconductorand/or an organic p-type semiconductor.
 16. The photoelectric conversionelement according to claim 14, wherein the infrared photoelectricconversion unit comprises one or more selected from the group consistingof a hole transport layer, an electron transport layer, a hole blockinglayer, and an electron blocking layer between the electrode and theorganic infrared photoelectric conversion film.
 17. The photoelectricconversion element according to claim 14, wherein in the infraredphotoelectric conversion unit, a local maximum absorption wavelength anda maximum absorption wavelength of optical absorption spectra in theinfrared region are 800 nm or more and 2500 nm or less.
 18. Thephotoelectric conversion element according to claim 14, wherein thephotoelectric conversion element further comprises a visiblephotoelectric conversion unit having sensitivity to a light in thevisible region.